XML Query Use Cases

1 Use Cases for XML Queries

The use cases listed below were created by the XML Query Working Group to illustrate important applications for an XML query language. Each use case is focused on a specific application area, and contains a Document Type Definition (DTD) and example input data. Each use case specifies a set of queries that might be applied to the input data, and the expected results for each query. Since the English description of each query is concise, the expected results form an important part of the definition of each query, specifying the expected output format. These use cases were originally published as part of the W3C XML Query Requirements document, without solutions in concrete query languages. Now it is being republished with solutions for XQuery.

Several implementors have asked that we make the queries from these use cases available in a separate file to make it easier for them to test their parsers. These queries may be found in [Use Case Sample Queries]. Also, the queries from the XQuery specification itself have been made available in [XQuery Sample Queries].

Some of the use cases assume that input is provided in the form of one or more documents with specific names such as "http://www.bn.com/bib.xml". Other use cases are based on implicit (unnamed) input documents. The input environment for each use case is stated in its Document Type Definition (DTD) section.

These use cases represent a snapshot of an ongoing work. Some important application areas are not yet adequately covered by a use case. The XML Query Working Group reserves the right to add, delete, or modify individual queries or whole use cases as the work progresses. The presence of a query in this set of use cases does not necessarily indicate that the query will be expressible in the XML Query Language(s) to be created by the XML Query Working Group.

1.1 Use Case "XMP": Experiences and Exemplars

This use case contains several example queries that illustrate requirements gathered from the database and document communities.

1.1.1 Document Type Definitions (DTD)

Most of the example queries in this use case are based on a bibliography document named "http://www.bn.com/bib.xml" with the following DTD:

<!ELEMENT bib  (book* )>
<!ELEMENT book  (title,  (author+ | editor+ ), publisher, price )>
<!ATTLIST book  year CDATA  #REQUIRED >
<!ELEMENT author  (last, first )>
<!ELEMENT editor  (last, first, affiliation )>
<!ELEMENT title  (#PCDATA )>
<!ELEMENT last  (#PCDATA )>
<!ELEMENT first  (#PCDATA )>
<!ELEMENT affiliation  (#PCDATA )>
<!ELEMENT publisher  (#PCDATA )>
<!ELEMENT price  (#PCDATA )>

1.1.2 Sample Data

Here is the data found at www.bn.com/bib.xml:

<bib>
    <book year="1994">
        <title>TCP/IP Illustrated</title>
        <author><last>Stevens</last><first>W.</first></author>
        <publisher>Addison-Wesley</publisher>
        <price> 65.95</price>
    </book>
 
    <book year="1992">
        <title>Advanced Programming in the Unix environment</title>
        <author><last>Stevens</last><first>W.</first></author>
        <publisher>Addison-Wesley</publisher>
        <price>65.95</price>
    </book>
 
    <book year="2000">
        <title>Data on the Web</title>
        <author><last>Abiteboul</last><first>Serge</first></author>
        <author><last>Buneman</last><first>Peter</first></author>
        <author><last>Suciu</last><first>Dan</first></author>
        <publisher>Morgan Kaufmann Publishers</publisher>
        <price> 39.95</price>
    </book>
 
    <book year="1999">
        <title>The Economics of Technology and Content for Digital TV</title>
        <editor>
               <last>Gerbarg</last><first>Darcy</first>
                <affiliation>CITI</affiliation>
        </editor>
            <publisher>Kluwer Academic Publishers</publisher>
        <price>129.95</price>
    </book>
 
</bib>

1.1.3 DTD for Q5

Q5 also uses information on book reviews and prices from a separate data source named "http://www.amazon.com/reviews.xml" with the following DTD:

<!ELEMENT reviews (entry*)>
<!ELEMENT entry   (title, price, review)>
<!ELEMENT title   (#PCDATA)>
<!ELEMENT price   (#PCDATA)>
<!ELEMENT review  (#PCDATA)>

1.1.4 Sample Data for Q5

Here are the contents of "http://www.amazon.com/reviews.xml":

<reviews>
    <entry>
        <title>Data on the Web</title>
        <price>34.95</price>
        <review>
               A very good discussion of semi-structured database
               systems and XML.
        </review>
    </entry>
    <entry>
        <title>Advanced Programming in the Unix environment</title>
        <price>65.95</price>
        <review>
               A clear and detailed discussion of UNIX programming.
        </review>
    </entry>
    <entry>
        <title>TCP/IP Illustrated</title>
        <price>65.95</price>
        <review>
               One of the best books on TCP/IP.
        </review>
    </entry>
</reviews>

1.1.5 DTD for Q9

Q9 uses an input document named "books.xml", with the following DTD:

<!ELEMENT chapter (title, section*)>
<!ELEMENT section (title, section*)>
<!ELEMENT title (#PCDATA)>

1.1.6 Data for Q9

Here are the contents of books.xml:

<chapter>
    <title>Data Model</title>
    <section>
        <title>Syntax For Data Model</title>
    </section>
    <section>
        <title>XML</title>
        <section>
            <title>Basic Syntax</title>
        </section>
        <section>
            <title>XML and Semistructured Data</title>
        </section>
    </section>
</chapter>

1.1.7 DTD for Q10

Q10 uses an input document named "prices.xml", with the following DTD:

<!ELEMENT prices (book*)>
<!ELEMENT book (title, source, price)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT source (#PCDATA)>
<!ELEMENT price (#PCDATA)>

1.1.8 Data for Q10

Here are the contents of prices.xml:

<prices>
    <book>
        <title>Advanced Programming in the Unix environment</title>
        <source>www.amazon.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title>Advanced Programming in the Unix environment </title>
        <source>www.bn.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title> TCP/IP Illustrated </title>
        <source>www.amazon.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title> TCP/IP Illustrated </title>
        <source>www.bn.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title>Data on the Web</title>
        <source>www.amazon.com</source>
        <price>34.95</price>
    </book>
    <book>
        <title>Data on the Web</title>
        <source>www.bn.com</source>
        <price>39.95</price>
    </book>
</prices>

1.1.9 Queries and Results

1.1.9.1 Q1

List books published by Addison-Wesley after 1991, including their year and title.

Solution in XQuery:

<bib>
 {
  for $b in document("http://www.bn.com")/bib/book
  where $b/publisher = "Addison-Wesley" and $b/@year > 1991
  return
    <book year={ $b/@year }>
     { $b/title }
    </book>
 }
</bib>

Expected Result:

<bib>
    <book year="1994">
        <title>TCP/IP Illustrated</title>
    </book>
    <book year="1992">
        <title>Advanced Programming in the Unix environment</title>
    </book>
</bib>

1.1.9.2 Q2

Create a flat list of all the title-author pairs, with each pair enclosed in a "result" element.

Solution in XQuery:

<results>
  {
    for $b in document("http://www.bn.com")/bib/book,
        $t in $b/title,
        $a in $b/author
    return
        <result>
            { $t }    
            { $a }
        </result>
  }
</results>

Expected Result:

<results>
    <result>
        <title>TCP/IP Illustrated</title>
        <author>
            <last>Stevens</last>
            <first>W.</first>
        </author>
    </result>
    <result>
        <title>Advanced Programming in the Unix environment</title>
        <author>
            <last>Stevens</last>
            <first>W.</first>
        </author>
    </result>
    <result>
        <title>Data on the Web</title>
        <author>
            <last>Abiteboul</last>
            <first>Serge</first>
        </author>
    </result>
    <result>
        <title>Data on the Web</title>
        <author>
            <last>Buneman</last>
            <first>Peter</first>
        </author>
    </result>
    <result>
        <title>Data on the Web</title>
        <author>
            <last>Suciu</last>
            <first>Dan</first>
        </author>
    </result>
</results>

1.1.9.3 Q3

For each book in the bibliography, list the title and authors, grouped inside a "result" element.

Solution in XQuery:

<results>
  {
    for $b in document("http://www.bn.com")/bib/book
    return
        <result>
            { $b/title }
            {
                for $a in $b/author
                return $a
            }
        </result>
  }
</results>

Expected Result:

<results>
    <result>
        <title>TCP/IP Illustrated</title>
        <author>
            <last>Stevens</last>
            <first>W.</first>
        </author>
    </result>
    <result>
        <title>Advanced Programming in the Unix environment</title>
        <author>
            <last>Stevens</last>
            <first>W.</first>
        </author>
    </result>
    <result>
        <title>Data on the Web</title>
        <author>
            <last>Abiteboul</last>
            <first>Serge</first>
        </author>
        <author>
            <last>Buneman</last>
            <first>Peter</first>
        </author>
        <author>
            <last>Suciu</last>
            <first>Dan</first>
        </author>
    </result>
    <result>
        <title>The Economics of Technology and Content for Digital TV</title>
    </result>
</results>

1.1.9.4 Q4

For each author in the bibliography, list the author's name and the titles of all books by that author, grouped inside a "result" element.

Solution in XQuery:

<results>
  {
    for $a in distinct-values(document("http://www.bn.com")//author)
    return
        <result>
            { $a }
            {
                for $b in document("http://www.bn.com")/bib/book
		where value-equals($b/author,$a)
                return $b/title
            }
        </result>
  }
</results>

In the above query, value-equals() tests to see if the two nodes have the same structure and values.

Expected Result:

<results>
    <result>
        <author>
            <last>Stevens</last>
            <first>W.</first>
        </author>
        <title>TCP/IP Illustrated</title>
        <title>Advanced Programming in the Unix environment</title>
    </result>
    <result>
        <author>
            <last>Abiteboul</last>
            <first>Serge</first>
        </author>
        <title>Data on the Web</title>
    </result>
    <result>
        <author>
            <last>Buneman</last>
            <first>Peter</first>
        </author>
        <title>Data on the Web</title>
    </result>
    <result>
        <author>
            <last>Suciu</last>
            <first>Dan</first>
        </author>
        <title>Data on the Web</title>
    </result>
</results>

1.1.9.5 Q5

For each book found at both bn.com and amazon.com, list the title of the book and its price from each source.

Solution in XQuery:

<books-with-prices>
  {
    for $b in document("www.bn.com/bib.xml")//book,
        $a in document("www.amazon.com/reviews.xml")//entry
    where $b/title = $a/title
    return
        <book-with-prices>
            { $b/title }
            <price-amazon>{ $a/price/text() }</price-amazon>
            <price-bn>{ $b/price/text() }</price-bn>
        </book-with-prices>
  }
</books-with-prices>

Expected Result:

<books-with-prices>
    <book-with-prices>
        <title>TCP/IP Illustrated</title>
        <price-amazon>65.95</price-amazon>
        <price-bn> 65.95</price-bn>
    </book-with-prices>
    <book-with-prices>
        <title>Advanced Programming in the Unix environment</title>
        <price-amazon>65.95</price-amazon>
        <price-bn>65.95</price-bn>
    </book-with-prices>
    <book-with-prices>
        <title>Data on the Web</title>
        <price-amazon>34.95</price-amazon>
        <price-bn> 39.95</price-bn>
    </book-with-prices>
</books-with-prices>

1.1.9.6 Q6

For each book that has at least one author, list the title and first two authors, and an empty "et-al" element if the book has additional authors.

Solution in XQuery:

<bib>
  {
    for $b in document("www.bn.com/bib.xml")//book
    where count($b/author) > 0
    return
        <book>
            { $b/title }
            {
                for $a in $b/author[position()<=2]  
                return $a
            }
            {
                if (count($b/author) > 2)
                then <et-al/>
                else ()
            }
        </book>
  }
</bib>

Expected Result:

<bib>
    <book>
        <title>TCP/IP Illustrated</title>
        <author>
            <last>Stevens</last>
            <first>W.</first>
        </author>
    </book>
    <book>
        <title>Advanced Programming in the Unix environment</title>
        <author>
            <last>Stevens</last>
            <first>W.</first>
        </author>
    </book>
    <book>
        <title>Data on the Web</title>
        <author>
            <last>Abiteboul</last>
            <first>Serge</first>
        </author>
        <author>
            <last>Buneman</last>
            <first>Peter</first>
        </author>
        <et-al/>
    </book>
</bib>

1.1.9.7 Q7

List the titles and years of all books published by Addison-Wesley after 1991, in alphabetic order.

Solution in XQuery:

<bib>
  {
    for $b in document("www.bn.com/bib.xml")//book
    where $b/publisher = "Addison-Wesley" and $b/@year > "1991"
    return
        <book>
            { $b/@year }
            { $b/title }
        </book>
    sortby (title)
  }
</bib>

Expected Result:

<bib>
    <book year="1992">
        <title>Advanced Programming in the Unix environment</title>
    </book>
    <book year="1994">
        <title>TCP/IP Illustrated</title>
    </book>
</bib>

1.1.9.8 Q8

Find books in which some element has a tag ending in "or" and the same element contains the string "Suciu" (at any level of nesting). For each such book, return the title and the qualifying element.

Solution in XQuery:

for $b in document("www.bn.com/bib.xml")//book,
    $e in $b/*[contains(string(.), "Suciu")]
where ends_with(local-name($e), "or")
return
    <book>
        { $b/title }
        { $e }
    </book>

In the above solution, name() and ends_with() are functions defined in the Functions and Operators document.

Expected Result:

<book>
        <title>Data on the Web</title>
        <author>
            <last>Suciu</last>
            <first>Dan</first>
        </author>
 </book>

1.1.9.9 Q9

In the document "books.xml", find all section or chapter titles that contain the word "XML", regardless of the level of nesting.

Solution in XQuery:

<results>
  {
    for $t in document("books.xml")//chapter/title 
              union document("books.xml")//section/title
    where contains($t/text(), "XML")
    return $t
  }
</results>

Expected Result:

<results>
    <title>XML</title>
    <title>XML and Semistructured Data</title>
</results>

1.1.9.10 Q10

In the document "prices.xml", find the minimum price for each book, in the form of a "minprice" element with the book title as its title attribute.

Solution in XQuery:

<results>
  {
    let $doc := document("prices.xml")
    for $t in distinct-values($doc//book/title)
    let $p := $doc//book[title = $t]/price
    return
      <minprice title={ $t/text() }>
        <price>{ min(decimal($p/text())) }</price>
      </minprice>
  }
</results>

Expected Result:

<results>
    <minprice title="Advanced Programming in the Unix environment">
        <price>65.95</price>
    </minprice>
    <minprice title="TCP/IP Illustrated">
        <price>65.95</price>
    </minprice>
    <minprice title="Data on the Web">
        <price>34.95</price>
    </minprice>
</results>

1.1.9.11 Q11

For each book with an author, return the book with its title and authors. For each book with an editor, return a reference with the book title and the editor's affiliation.

Solution in XQuery:

<bib>
    {
        for $b in document("www.bn.com/bib.xml")//book[author]
        return
            <book>
                { $b/title }
                { $b/author }
            </book>
    }
    {
        for $b in document("www.bn.com/bib.xml")//book[editor]
        return
            <reference>
                { $b/title }
                <org>{ $b/editor/affiliation/text() }</org>
            </reference>
    }
</bib>

Expected Result:

<bib>
    <book>
        <title>TCP/IP Illustrated</title>
        <author>
            <last>Stevens</last>
            <first>W.</first>
        </author>
    </book>
    <book>
        <title>Advanced Programming in the Unix environment</title>
        <author>
            <last>Stevens</last>
            <first>W.</first>
        </author>
    </book>
    <book>
        <title>Data on the Web</title>
        <author>
            <last>Abiteboul</last>
            <first>Serge</first>
        </author>
        <author>
            <last>Buneman</last>
            <first>Peter</first>
        </author>
        <author>
            <last>Suciu</last>
            <first>Dan</first>
        </author>
    </book>
    <reference>
        <title>The Economics of Technology and Content for Digital TV</title>
        <org>CITI</org>
    </reference>
</bib>

1.1.9.12 Q12

Find pairs of books that have different titles but the same set of authors (possibly in a different order).

Solution in XQuery:

<bib>
  {
    for $book1 in document("www.bn.com/bib.xml")//book,
        $book2 in document("www.bn.com/bib.xml")//book
    let $aut1 := $book1/author sortby(last, first),
        $aut2 := $book2/author sortby(last, first)
    where $book1 precedes $book2
    and not($book1/title = $book2/title)
    and sequence-value-equal($aut1, $aut2) 
    return
        <book-pair>
            { $book1/title }
            { $book2/title }
        </book-pair>
  }
</bib>

Expected Result:

<bib>
       <book-pair>
               <title>TCP/IP Illustrated</title>
               <title>Advanced Programming in the Unix environment</title>
       </book-pair>
</bib>

The above solution uses a function, sequence-value-equal(), which compares sequences. Two sequences are equal if all items in corresponding positions in the two sequences are equal - if the sequences are node sequences, the values of the nodes are used for comparison.

1.2 Use Case "TREE": Queries that preserve hierarchy

Some XML document-types have a very flexible structure in which text is mixed with elements and many elements are optional. These document-types show a wide variation in structure from one document to another. In documents of these types, the ways in which elements are ordered and nested are usually quite important.

1.2.1 Description

An XML query language should have the ability to extract elements from documents while preserving their original hierarchy. This Use Case illustrates this requirement by means of a flexible document type named Book.

1.2.2 Document Type Definition (DTD)

This use case is based on an input document named "book.xml", with the following DTD:

<!DOCTYPE book [
  <!ELEMENT book (title, author+, section+)>
  <!ELEMENT title (#PCDATA)>
  <!ELEMENT author (#PCDATA)>
  <!ELEMENT section (title, (p | figure | section)* )>
  <!ATTLIST section
      id         ID    #IMPLIED
      difficulty CDATA #IMPLIED>
  <!ELEMENT p (#PCDATA)>
  <!ELEMENT figure (title, image)>
  <!ATTLIST figure
       width   CDATA   #REQUIRED
       height  CDATA   #REQUIRED >
  <!ELEMENT image EMPTY>
  <!ATTLIST image
       source  CDATA   #REQUIRED >
]>

1.2.3 Sample Data

The queries in this use case are based on the following sample data.

<?xml version="1.0"?>
<!DOCTYPE book SYSTEM "book.dtd">
<book>
  <title>Data on the Web</title>
  <author>Serge Abiteboul</author>
  <author>Peter Buneman</author>
  <author>Dan Suciu</author>
  <section id="intro" difficulty="easy" >
    <title>Introduction</title>
    <p>Text ... </p>
    <section>
      <title>Audience</title>
      <p>Text ... </p>
    </section>
    <section>
      <title>Web Data and the Two Cultures</title>
      <p>Text ... </p>
      <figure height="400" width="400">
        <title>Traditional client/server architecture</title>
        <image source="csarch.gif"/>
      </figure>
      <p>Text ... </p>
    </section>
  </section>
  <section id="syntax" difficulty="medium" >
    <title>A Syntax For Data</title>
    <p>Text ... </p>
    <figure height="200" width="500">
      <title>Graph representations of structures</title>
      <image source="graphs.gif"/>
    </figure>
    <p>Text ... </p>
    <section>
      <title>Base Types</title>
      <p>Text ... </p>
    </section>
    <section>
      <title>Representing Relational Databases</title>
      <p>Text ... </p>
      <figure height="250" width="400">
        <title>Examples of Relations</title>
        <image source="relations.gif"/>
      </figure>
    </section>
    <section>
      <title>Representing Object Databases</title>
      <p>Text ... </p>
    </section>       
  </section>
</book>

1.2.4 Queries and Results

1.2.4.1 Q1

Prepare a (nested) table of contents for Book1, listing all the sections and their titles. Preserve the original attributes of each <section> element, if any.

Solution in XQuery:

<toc>
  {
    let $b := document("book1.xml")
    return
        filter($b//section | $b//section/title | $b//section/title/text())
  }
</toc>

Expected Result:

<toc>
    <section id="intro" difficulty="easy">
        <title>Introduction</title>
        <section>
            <title>Audience</title>
        </section>
        <section>
            <title>Web Data and the Two Cultures</title>
        </section>
    </section>
    <section id="syntax" difficulty="medium">
        <title>A Syntax For Data</title>
        <section>
            <title>Base Types</title>
        </section>
        <section>
            <title>Representing Relational Databases</title>
        </section>
        <section>
            <title>Representing Object Databases</title>
        </section>
    </section>
</toc>

1.2.4.2 Q2

Prepare a (flat) figure list for Book1, listing all the figures and their titles. Preserve the original attributes of each <figure> element, if any.

Solution in XQuery:

<figlist>
  {
    for $f in document("book1.xml")//figure
    return
        <figure>
            { $f/@* }
            { $f/title }
        </figure>
  }
</figlist>

Expected Result:

<figlist>
    <figure  height="400" width="400">
        <title>Traditional client/server architecture</title>
    </figure>
    <figure  height="200" width="500">
        <title>Graph representations of structures</title>
    </figure>
    <figure  height="250" width ="400">
        <title>Examples of Relations</title>
    </figure>
</figlist>

1.2.4.3 Q3

How many sections are in Book1, and how many figures?

Solution in XQuery:

<section_count>{ count(document("book1.xml")//section) }</section_count>, 
<figure_count>{ count(document("book1.xml")//figure) }</figure_count>

Expected Result:

<section_count>7</section_count>
<figure_count>3</figure_count>

1.2.4.4 Q4

How many top-level sections are in Book1?

Solution in XQuery:

<top_section_count>
 { 
   count(document("book1.xml")/book/section) 
 }
</top_section_count>

Expected Result:

<top_section_count>2</top_section_count>

1.2.4.5 Q5

Make a flat list of the section elements in Book1. In place of its original attributes, each section element should have two attributes, containing the title of the section and the number of figures immediately contained in the section.

Solution in XQuery:

<section_list>
  {
    for $s in document("book1.xml")//section
    let $f := $s/figure
    return
        <section title={ $s/title/text() } figcount={ count($f) }/>
  }
</section_list>

Expected Result:

<section_list>
    <section title="Introduction" figcount="0"/>
    <section title="A Syntax For Data" figcount="1"/>
    <section title="Audience" figcount="0"/>
    <section title="Web Data and the Two Cultures" figcount="1"/>
    <section title="Base Types" figcount="0"/>
    <section title="Representing Relational Databases" figcount="1"/>
    <section title="Representing Object Databases" figcount="0"/>
</section_list>

1.2.4.6 Q6

Make a nested list of the section elements in Book1, preserving their original attributes and hierarchy. Inside each section element, include the title of the section and an element that includes the number of figures immediately contained in the section.

Solution in XQuery:

define function section_summary(element $s) returns element
{
    <section>
        { $s/@* }
        { $s/title }
        <figcount>{ count($s/figure) }</figcount>
        {
            for $ss in $s/section
            return section_summary($ss)
        }
    </section>
}

<toc>
  {
    for $s in document("book1.xmll")//section
    return section_summary($s)
  }
</toc>

Expected Result:

<toc>
    <section>
        <title>Introduction</title>
        <figcount>0</figcount>
        <section>
            <title>Audience</title>
            <figcount>0</figcount>
        </section>
        <section>
            <title>Web Data and the Two Cultures</title>
            <figcount>1</figcount>
        </section>
    </section>
    <section>
        <title>A Syntax For Data</title>
        <figcount>1</figcount>
        <section>
            <title>Base Types</title>
            <figcount>0</figcount>
        </section>
        <section>
            <title>Representing Relational Databases</title>
            <figcount>1</figcount>
        </section>
        <section>
            <title>Representing Object Databases</title>
            <figcount>0</figcount>
        </section>
    </section>
    <section>
        <title>Audience</title>
        <figcount>0</figcount>
    </section>
    <section>
        <title>Web Data and the Two Cultures</title>
        <figcount>1</figcount>
    </section>
    <section>
        <title>Base Types</title>
        <figcount>0</figcount>
    </section>
    <section>
        <title>Representing Relational Databases</title>
        <figcount>1</figcount>
    </section>
    <section>
        <title>Representing Object Databases</title>
        <figcount>0</figcount>
    </section>
</toc>

1.3 Use Case "SEQ" - Queries based on Sequence

This use case illustrates queries based on the sequence in which elements appear in a document.

1.3.1 Description

Although sequence is not significant in most traditional database systems or object systems, it can be quite significant in structured documents. This use case presents a series of queries based on a medical report.

1.3.2 Document Type Definition (DTD)

This use case is based on a medical report using the HL7 Patient Record Architecture. We simplify the DTD in this example, using only what is needed to understand the queries.

<!DOCTYPE report [
  <!ELEMENT report (section*)>
  <!ELEMENT section (section.title, section.content)>
  <!ELEMENT section.title  (#PCDATA )>
  <!ELEMENT section.content  (#PCDATA | anesthesia | prep 
                            | incision | action | observation )*>
  <!ELEMENT anesthesia (#PCDATA)>
  <!ELEMENT prep ( (#PCDATA | action)* )>
  <!ELEMENT incision ( (#PCDATA | geography | instrument)* )>
  <!ELEMENT action ( (#PCDATA | instrument )* )>
  <!ELEMENT observation (#PCDATA)>
  <!ELEMENT geography (#PCDATA)>
  <!ELEMENT instrument (#PCDATA)>
]>

1.3.3 Sample Data

The queries in this use case are based on the following sample data.

<report>
  <section>
    <section.title>Procedure</section.title>
     <section.content>
      The patient was taken to the operating room where she was placed
      in supine position and
      <anesthesia>induced under general anesthesia.</anesthesia>
      <prep> 
        <action>A Foley catheter was placed to decompress the bladder</action>
        and the abdomen was then prepped and draped in sterile fashion.
      </prep>  
      <incision>
        A curvilinear incision was made
        <geography>in the midline immediately infraumbilical</geography>
        and the subcutaneous tissue was divided
        <instrument>using electrocautery.</instrument>
      </incision>
      The fascia was identified and
      <action>#2 0 Maxon stay sutures were placed on each side of the midline.
      </action>
      <incision>
        The fascia was divided using
        <instrument>electrocautery</instrument>
        and the peritoneum was entered.
      </incision>
      <observation>The small bowel was identified.</observation>
      and
      <action>
        the
        <instrument>Hasson trocar</instrument>
        was placed under direct visualization.
      </action>
      <action>
        The
        <instrument>trocar</instrument>
        was secured to the fascia using the stay sutures.
      </action>
     </section.content>
  </section>
</report>

1.3.4 Queries and Results

1.3.4.1 Q1

In the Procedure section of Report1, what Instruments were used in the second Incision?

Solution in XQuery:

for $s in document("report1.xml")//section[section.title = "Procedure"]
return ($s//incision)[2]/instrument

Expected Result:

<instrument>electrocautery</instrument>

1.3.4.2 Q2

In the Procedure section of Report1, what are the first two Instruments to be used?

Solution in XQuery:

for $s in document("report1.xml")//section[section.title = "Procedure"]
return ($s//instrument)[position()<=2]

Expected Result:

<instrument>using electrocautery.</instrument>
<instrument>electrocautery</instrument>

1.3.4.3 Q3

In Report1, what Instruments were used in the first two Actions after the second Incision?

Solution in XQuery:

let $i2 := (document("report1.xml")//incision)[2]
for $a in (document("report1.xml")//action)[. follows $i2][position()<=2]
return $a//instrument

Expected Result:

<instrument>Hasson trocar</instrument>
<instrument>trocar</instrument>

1.3.4.4 Q4

In Report1, find "Procedure" sections where no Anesthesia element occurs before the first Incision

Solution in XQuery:

for $p in //procedure
where some $i in $proc//incision satisfies
        empty($proc//anesthesia[. precedes $i])
return $p

Expected Result:

<result />

(No sections satisfy Q4, thankfully.)

1.3.4.5 Q5

In Report1, what happened between the first Incision and the second Incision?

Solution in XQuery:

<critical_sequence>
 {
    let $proc := //procedure[1]
    for $n in $proc//node()
    where $n follows ($proc//incision)[1]
      and $n precedes ($proc//incision)[2]
    return $n
 }
</critical_sequence>

Expected Result:

<action>#2 0 Maxon stay sutures were placed on each side of the midline.</action>

1.4 Use Case "R" - Access to Relational Data

One important use of an XML query language will be to access data stored in relational databases. This use case describes one possible way in which this access might be accomplished.

1.4.1 Description

A relational database system might present a view in which each table (relation) takes the form of an XML document. One way to represent a database table as an XML document is to allow the document element to represent the table itself, and each row (tuple) inside the table to be represented by a nested element. Inside the tuple-elements, each column is in turn represented by a nested element. Columns that allow null values are represented by optional elements, and a missing element denotes a null value.

As an example, consider a relational database used by an online auction. The auction maintains a USERS table containing information on registered users, each identified by a unique userid, who can either offer items for sale or bid on items. An ITEMS table lists items currently or recently for sale, with the userid of the user who offered each item. A BIDS table contains all bids on record, keyed by the userid of the bidder and the item number of the item to which the bid applies.

The three tables used by the online auction are below, with their column-names indicated in parentheses.

USERS ( USERID, NAME, RATING )

ITEMS ( ITEMNO, DESCRIPTION, OFFERED_BY, START_DATE, END_DATE, RESERVE_PRICE )

BIDS ( USERID, ITEMNO, BID, BID_DATE )

1.4.2 Document Type Definition (DTD)

This use case is based on three separate input documents named users.xml, items.xml, and bids.xml. Each of the documents represents one of the tables in the relational database described above, using the following DTDs:

<!DOCTYPE users [
  <!ELEMENT users   (user_tuple*)>
  <!ELEMENT user_tuple (userid, name, rating?)>
  <!ELEMENT userid  (#PCDATA)>
  <!ELEMENT name    (#PCDATA)>
  <!ELEMENT rating  (#PCDATA)>
]>

<!DOCTYPE items [
  <!ELEMENT items       (item_tuple*)>
  <!ELEMENT item_tuple  (itemno, description, offered_by, 
                              start_date?, end_date?, reserve_price? )>
  <!ELEMENT itemno      (#PCDATA)>
  <!ELEMENT description (#PCDATA)>
  <!ELEMENT offered_by  (#PCDATA)>
  <!ELEMENT start_date  (#PCDATA)>
  <!ELEMENT end_date    (#PCDATA)>
  <!ELEMENT reserve_price (#PCDATA)>
]>

<!DOCTYPE bids [
  <!ELEMENT bids      (bid_tuple*)>
  <!ELEMENT bid_tuple (userid, itemno, bid, bid_date)>
  <!ELEMENT userid    (#PCDATA)>
  <!ELEMENT itemno    (#PCDATA)>
  <!ELEMENT bid       (#PCDATA)>
  <!ELEMENT bid_date  (#PCDATA)>
]>

1.4.3 Sample Data

The following tables contain example data. Representation of this data in the DTD of this Use Case is straightforward but rather bulky, and is not included here.

USERS
USERID	NAME	RATING
U01	Tom Jones	B
U02	Mary Doe	A
U03	Dee Linquent	D
U04	Roger Smith	C
U05	Jack Sprat	B
U06	Rip Van Winkle	B

ITEMS
ITEMNO	DESCRIPTION	OFFERED_BY	START_DATE	END_DATE	RESERVE_PRICE
1001	Red Bicycle	U01	99-01-05	99-01-20	40
1002	Motorcycle	U02	99-02-11	99-03-15	500
1003	Old Bicycle	U02	99-01-10	99-02-20	25
1004	Tricycle	U01	99-02-25	99-03-08	15
1005	Tennis Racket	U03	99-03-19	99-04-30	20
1006	Helicopter	U03	99-05-05	99-05-25	50000
1007	Racing Bicycle	U04	99-01-20	99-02-20	200
1008	Broken Bicycle	U01	99-02-05	99-03-06	25

BIDS
USERID	ITEMNO	BID	BID_DATE
U02	1001	35	99-01-07
U04	1001	40	99-01-08
U02	1001	45	99-01-11
U04	1001	50	99-01-13
U02	1001	55	99-01-15
U01	1002	400	99-02-14
U02	1002	600	99-02-16
U03	1002	800	99-02-17
U04	1002	1000	99-02-25
U02	1002	1200	99-03-02
U04	1003	15	99-01-22
U05	1003	20	99-02-03
U01	1004	40	99-03-05
U03	1007	175	99-01-25
U05	1007	200	99-02-08
U04	1007	225	99-02-12

1.4.4 Queries and Results

The following results assume that the queries were executed on Feb. 1, 1999.

1.4.4.1 Q1

List the item number and description of all bicycles that currently have an auction in progress, ordered by item number.

Solution in XQuery:

<result>
  {
    for $i in document("items.xml")//item_tuple
    where $i/start_date <= date()
      and $i/end_date >= date() 
      and contains($i/description, "Bicycle")
    return
        <item_tuple>
            { $i/itemno }
            { $i/description }
        </item_tuple>
    sortby (itemno)
  }
</result>

Note:

This query presumes that the date() function returns the current system date. In the current [Fando], there is no function to return the system date.

Expected Result:

<result>
    <item_tuple>
        <itemno>1003</itemno>
        <description>Old Bicycle</description>
    </item_tuple>
    <item_tuple>
        <itemno>1007</itemno>
        <description>Racing Bicycle</description>
    </item_tuple>
</result>

1.4.4.2 Q2

For all bicycles, list the item number, description, and highest bid (if any), ordered by item number.

Solution in XQuery:

<result>
  {
    for $i in document("items.xml")//item_tuple
    let $b := document("bids.xml")//bid_tuple[itemno = $i/itemno]
    where contains($i/description, "Bicycle")
    return
        <item_tuple>
            { $i/itemno }
            { $i/description }
            <high_bid>{ max($b/bid) }</high_bid>
        </item_tuple>
    sortby(itemno)
  }
</result>

Expected Result:

<result>
    <item_tuple>
        <itemno>1001</itemno>
        <description>Red Bicycle</description>
        <high_bid>
            <bid>55</bid>
        </high_bid>
    </item_tuple>
    <item_tuple>
        <itemno>1003</itemno>
        <description>Old Bicycle</description>
        <high_bid>
            <bid>20</bid>
        </high_bid>
    </item_tuple>
    <item_tuple>
        <itemno>1007</itemno>
        <description>Racing Bicycle</description>
        <high_bid>
            <bid>225</bid>
        </high_bid>
    </item_tuple>
    <item_tuple>
        <itemno>1008</itemno>
        <description>Broken Bicycle</description>
        <high_bid/>
    </item_tuple>
</result>

1.4.4.3 Q3

Find cases where a user with a rating worse (alphabetically, greater) than "C" is offering an item with a reserve price of more than 1000.

Solution in XQuery:

<result>
  {
    for $u in document("users.xml")//user_tuple
    for $i in document("items.xml")//item_tuple
    where $u/rating > "C" 
       and $i/reserve_price > 1000 
       and $i/offered_by = $u/userid
    return
        <warning>
            { $u/name }
            { $u/rating }
            { $i/description }
            { $i/reserve_price }
        </warning>
  }
</result>

Expected Result:

<result>
    <warning>
        <name>Dee Linquent</name>
        <rating>D</rating>
        <description>Helicopter</description>
        <reserve_price>50000</reserve_price>
    </warning>
</result>

1.4.4.4 Q4

List item numbers and descriptions of items that have no bids.

Solution in XQuery:

<result>
  {
    for $i in document("items.xml")//item_tuple
    where not(some $b in document("bids.xml")//bid_tuple 
                        satisfies $b/itemno = $i/itemno)
    return
        <no_bid_item>
            { $i/itemno }
            { $i/description }
        </no_bid_item>
  }
</result>

Expected Result:

<result>
    <no_bid_item>
        <itemno>1005</itemno>
        <description>Tennis Racket</description>
    </no_bid_item>
    <no_bid_item>
        <itemno>1006</itemno>
        <description>Helicopter</description>
    </no_bid_item>
    <no_bid_item>
        <itemno>1008</itemno>
        <description>Broken Bicycle</description>
    </no_bid_item>
</result>

1.4.4.5 Q5

For bicycle(s) offered by Tom Jones, list the item number, description, highest bid (if any), and name of the highest bidder, ordered by item number.

Solution in XQuery:

<result>
  {
    for $seller in document("users.xml")//user_tuple,
        $buyer in  document("users.xml")//user_tuple,
        $item in  document("items.xml")//item_tuple,
        $highbid in  document("bids.xml")//bid_tuple
    where $seller/name = "Tom Jones" 
      and $seller/userid = $item/offered_by 
      and contains($item/description, "Bicycle") 
      and $item/itemno = $highbid/itemno 
      and $highbid/userid = $buyer/userid 
      and $highbid/bid = max(document("bids.xml")//bid_tuple
                               [itemno = $item/itemno]/bid)
    return
        <jones_bike>
            { $item/itemno }
            { $item/description }
            <high_bid>{ $highbid/bid }</high_bid>
            <high_bidder>{ $buyer/name }</high_bidder>
        </jones_bike>
    sortby(itemno)
  }
</result>

The following alternate solution uses the unordered function to inform the query processor that the order of the lists in the for clause is not significant, which means that the tuples can be generated in any order. This can enable better optimization.

Alternate Solution in XQuery:

<result>
  {
    for $seller in unordered(document("users.xml")//user_tuple),
        $buyer in  unordered(document("users.xml")//user_tuple),
        $item in  unordered(document("items.xml")//item_tuple),
        $highbid in  unordered(document("bids.xml")//bid_tuple)
    where $seller/name = "Tom Jones" 
      and $seller/userid = $item/offered_by 
      and contains($item/description, "Bicycle") 
      and $item/itemno = $highbid/itemno 
      and $highbid/userid = $buyer/userid 
      and $highbid/bid = max(document("bids.xml")//bid_tuple 
                               [itemno = $item/itemno]/bid)
    return
        <jones_bike>
            { $item/itemno }
            { $item/description }
            <high_bid>{ $highbid/bid }</high_bid>
            <high_bidder>{ $buyer/name }</high_bidder>
        </jones_bike>
    sortby (itemno)
  }
</result>

Expected Result:

<result>
    <jones_bike>
        <itemno>1001</itemno>
        <description>Red Bicycle</description>
        <high_bid>
            <bid>55</bid>
        </high_bid>
        <high_bidder>
            <name>Mary Doe</name>
        </high_bidder>
    </jones_bike>
</result>

1.4.4.6 Q6

For each item whose highest bid is more than twice its reserve price, list the item number, description, reserve price, and highest bid.

Solution in XQuery:

<result>
  {
    for $item in document("items.xml")//item_tuple
    let $b := document("bids.xml")//bid_tuple[itemno = $item/itemno]
    where $item/reserve_price * 2 < max($b/bid)
    return
        <successful_item>
            { $item/itemno }
            { $item/description }
            { $item/reserve_price }
            <high_bid>{ max($b/bid) }</high_bid>
        </successful_item>
 }
</result>

Expected Result:

<result>
    <successful_item>
        <itemno>1002</itemno>
        <description>Motorcycle</description>
        <reserve_price>500</reserve_price>
        <high_bid>
            <bid>1200</bid>
        </high_bid>
    </successful_item>
    <successful_item>
        <itemno>1004</itemno>
        <description>Tricycle</description>
        <reserve_price>15</reserve_price>
        <high_bid>
            <bid>40</bid>
        </high_bid>
    </successful_item>
</result>

1.4.4.7 Q7

Find the highest bid ever made for a bicycle or tricycle.

Solution in XQuery:

let $allbikes := document("items.xml")//item_tuple
                    [contains(description, "Bicycle") 
                     or contains(description, "Tricycle")]
let $bikebids := document("bids.xml")//bid_tuple[itemno = $allbikes/itemno]
return
    <high_bid>
      { 
        max($bikebids/bid) 
      }
    </high_bid>

Expected Result:

<high_bid><bid>225</bid></high_bid>

1.4.4.8 Q8

How many items were actioned (auction ended) in March 1999?

Solution in XQuery:

let $item := document("items.xml")//item_tuple
  [end_date >= date("1999-03-01") and end_date <= date("1999-03-31")]
return
    <item_count>
      { 
        count($item) 
      }
    </item_count>

Expected Result:

<item_count>3</item_count>

1.4.4.9 Q9

List the number of items auctioned each month in 1999 for which data is available, ordered by month.

Solution in XQuery:

<result>
  {
    let $end_dates := document("items.xml")//item_tuple/end_date
    for $m in distinct-values(for $e in $end_dates return month($e))
    let $item := document("items.xml")
        //item_tuple[year(end_date) = 1999 and month(end_date) = $m]
    return
        <monthly_result>
            <month>{ $m }</month>
            <item_count>{ count($item) }</item_count>
        </monthly_result>
    sortby(month)
  }
</result>

Note:

In this example, month and year are functions that are not yet defined in our [FandO]

Expected Result:

<result>
  <monthly_result>
    <month> 1 </month>
    <item_count> 1 </item_count>
  </monthly_result>
  <monthly_result>
    <month> 2 </month>
    <item_count> 2 </item_count>
  </monthly_result>
  <monthly_result>
    <month> 3 </month>
    <item_count> 3 </item_count>
  </monthly_result>
  <monthly_result>
    <month> 4 </month>
    <item_count> 1 </item_count>
  </monthly_result>
  <monthly_result>
    <month> 5 </month>
    <item_count> 1 </item_count>
  </monthly_result>
</result>

1.4.4.10 Q10

For each item that has received a bid, list the item number, the highest bid, and the name of the highest bidder, ordered by item number.

Solution in XQuery:

<result>
  {
    for $highbid in document("bids.xml")//bid_tuple,
        $user in document("users.xml")//user_tuple
    where $user/userid = $highbid/userid 
      and $highbid/bid = max(document("bids.xml")//bid_tuple
                              [itemno = $highbid/itemno]/bid)
    return
        <high_bid>
            { $highbid/itemno }
            { $highbid/bid }
            <bidder>{ $user/name/text() }</bidder>
        </high_bid>
    sortby(itemno)
  }
</result>

Expected Result:

<result>
    <high_bid>
        <itemno>1001</itemno>
        <bid>55</bid>
        <bidder>Mary Doe</bidder>
    </high_bid>
    <high_bid>
        <itemno>1002</itemno>
        <bid>1200</bid>
        <bidder>Mary Doe</bidder>
    </high_bid>
    <high_bid>
        <itemno>1003</itemno>
        <bid>20</bid>
        <bidder>Jack Sprat</bidder>
    </high_bid>
    <high_bid>
        <itemno>1004</itemno>
        <bid>40</bid>
        <bidder>Tom Jones</bidder>
    </high_bid>
    <high_bid>
        <itemno>1007</itemno>
        <bid>225</bid>
        <bidder>Roger Smith</bidder>
    </high_bid>
</result>

1.4.4.11 Q11

List the item number and description of the item(s) that received the highest bid ever recorded, and the amount of that bid.

Solution in XQuery:

let $highbid := max(document("bids.xml")//bid_tuple/bid)
return
    <result>
      {
        for $item in document("items.xml")//item_tuple,
            $b in document("bids.xml")//bid_tuple[itemno = $item/itemno]
        where $b/bid = $highbid
        return
            <expensive_item>
                { $item/itemno }
                { $item/description }
                <high_bid>{ $highbid }</high_bid>
            </expensive_item>
      }
    </result>

Expected Result:

<result>
    <expensive_item>
        <itemno>1002</itemno>
        <description>Motorcycle</description>
        <high_bid>
            <bid>1200</bid>
        </high_bid>
    </expensive_item>
</result>

1.4.4.12 Q12

List the item number and description of the item(s) that received the largest number of bids, and the number of bids it (or they) received.

Solution in XQuery:

define function bid_summary ()
{
    for $i in distinct-values(document("bids.xml")//itemno)
    let $b := document("bids.xml")//bid_tuple[itemno = $i]
    return
        <bid_count>
            { $i }
            <nbids>{ count($b) }</nbids>
        </bid_count>
}

<result>
 {
    let $bid_counts := bid_summary(),
        $maxbids := max($bid_counts/nbids),
        $maxitemnos := $bid_counts[nbids=$max_bids]
    for $item in document("items.xml")//item_tuple,
        $bc in $bid_counts
    where $bc/nbids = $maxbids and $item/itemno = $bc/itemno
    return
        <popular_item>
            { $item/itemno }
            { $item/description }
            <bid_count>{ $bc/nbids/text() }</bid_count>
        </popular_item>
 }
</result>

Expected Result:

<result>
    <popular_item>
        <itemno>1001</itemno>
        <description>Red Bicycle</description>
        <bid_count>5</bid_count>
    </popular_item>
    <popular_item>
        <itemno>1002</itemno>
        <description>Motorcycle</description>
        <bid_count>5</bid_count>
    </popular_item>
</result>

1.4.4.13 Q13

For each user who has placed a bid, give the userid, name, number of bids, and average bid, in order by userid.

Solution in XQuery:

<result>
  {
    for $uid in distinct-values(document("bids.xml")//userid),
        $u in document("users.xml")//user_tuple[userid = $uid]
    let $b := document("bids.xml")//bid_tuple[userid = $uid]
    return
        <bidder>
            { $u/userid }
            { $u/name }
            <bidcount>{ count($b) }</bidcount>
            <avgbid>{ avg($b/bid) }</avgbid>
        </bidder>
    sortby(userid)
  }
</result>

Expected Result:

<result>
    <bidder>
        <userid>U01</userid>
        <name>Tom Jones</name>
        <bidcount>2</bidcount>
        <avgbid>220</avgbid>
    </bidder>
    <bidder>
        <userid>U02</userid>
        <name>Mary Doe</name>
        <bidcount>5</bidcount>
        <avgbid>387</avgbid>
    </bidder>
    <bidder>
        <userid>U03</userid>
        <name>Dee Linquent</name>
        <bidcount>2</bidcount>
        <avgbid>487</avgbid>
    </bidder>
    <bidder>
        <userid>U04</userid>
        <name>Roger Smith</name>
        <bidcount>5</bidcount>
        <avgbid>266</avgbid>
    </bidder>
    <bidder>
        <userid>U05</userid>
        <name>Jack Sprat</name>
        <bidcount>2</bidcount>
        <avgbid>110</avgbid>
    </bidder>
</result>

1.4.4.14 Q14

List item numbers and average bids for items that have received three or more bids, in descending order by average bid.

Solution in XQuery:

<result>
  {
    for $i in distinct-values(document("bids.xml")//itemno)
    let $b := document("bids.xml")//bid_tuple[itemno = $i]
    where count($b) >= 3
    return
        <popular_item>
            { $i }
            <avgbid>{ avg($b/bid) }</avgbid>
        </popular_item>
    sortby(avgbid descending)
  }
</result>

Expected Result:

<result>
    <popular_item>
        <itemno>1002</itemno>
        <avgbid>800</avgbid>
    </popular_item>
    <popular_item>
        <itemno>1007</itemno>
        <avgbid>200</avgbid>
    </popular_item>
    <popular_item>
        <itemno>1001</itemno>
        <avgbid>45</avgbid>
    </popular_item>
</result>

1.4.4.15 Q15

List names of users who have placed multiple bids of at least $100 each.

Solution in XQuery:

<result>
  {
    for $u in document("users.xml")//user_tuple
    let $b := document("bids.xml")//bid_tuple[userid = $u/userid and bid >= 100]
    where count($b) > 1
    return
        <big_spender>{ $u/name/text() }</big_spender>
  }
</result>

Expected Result:

<result>
    <big_spender>Mary Doe</big_spender>
    <big_spender>Dee Linquent</big_spender>
    <big_spender>Roger Smith</big_spender>
</result>

1.4.4.16 Q16

List all registered users in order by userid; for each user, include the userid, name, and an indication of whether the user is active (has at least one bid on record) or inactive (has no bid on record).

Solution in XQuery:

<result>
  {
    for $u in document("users.xml")//user_tuple
    let $b := document("bids.xml")//bid_tuple[userid = $u/userid]
    return
        <user>
            { $u/userid }
            { $u/name }
            {
                if (empty($b))
                then <status>inactive</status>
                else <status>active</status>
            }
        </user>
    sortby(userid)
  }
</result>

Expected Result:

<result>
    <user>
        <userid>U01</userid>
        <name>Tom Jones</name>
        <status>active</status>
    </user>
    <user>
        <userid>U02</userid>
        <name>Mary Doe</name>
        <status>active</status>
    </user>
    <user>
        <userid>U03</userid>
        <name>Dee Linquent</name>
        <status>active</status>
    </user>
    <user>
        <userid>U04</userid>
        <name>Roger Smith</name>
        <status>active</status>
    </user>
    <user>
        <userid>U05</userid>
        <name>Jack Sprat</name>
        <status>active</status>
    </user>
    <user>
        <userid>U06</userid>
        <name>Rip Van Winkle</name>
        <status>inactive</status>
    </user>
</result>

1.4.4.17 Q17

List the names of users, if any, who have bid on every item.

Solution in XQuery:

<frequent_bidder>
  {
    for $u in document("users.xml")//user_tuple
    where 
      every $item in document("items.xml")//item_tuple satisfies 
        some $b in document("bids.xml")//bid_tuple satisfies 
          ($item/itemno = $b/itemno and $u/userid = $b/userid)
    return
        $u/name
  }
</frequent_bidder>

Expected Result:

<frequent_bidder />

(No users satisfy Q17.)

1.4.4.18 Q18

List all users in alphabetic order by name. For each user, include descriptions of all the items (if any) that were bid on by that user, in alphabetic order.

Solution in XQuery:

<result>
  {
    for $u in document("users.xml")//user_tuple
    return
        <user>
            { $u/name }
            {
                for $b in distinct-values(document("bids.xml")//bid_tuple
                                             [userid = $u/userid]/itemno),
                    $i in document("items.xml")//item_tuple[itemno = $b]
                return
                    <bid_on_item>{ $i/description/text() }</bid_on_item>
                sortby(.)
            }
        </user>
    sortby(name)
  }
</result>

Expected Result:

<result>
    <user>
        <name>Dee Linquent</name>
        <bid_on_item>Motorcycle</bid_on_item>
        <bid_on_item>Racing Bicycle</bid_on_item>
    </user>
    <user>
        <name>Jack Sprat</name>
        <bid_on_item>Old Bicycle</bid_on_item>
        <bid_on_item>Racing Bicycle</bid_on_item>
    </user>
    <user>
        <name>Mary Doe</name>
        <bid_on_item>Motorcycle</bid_on_item>
        <bid_on_item>Red Bicycle</bid_on_item>
    </user>
    <user>
        <name>Rip Van Winkle</name>
    </user>
    <user>
        <name>Roger Smith</name>
        <bid_on_item>Motorcycle</bid_on_item>
        <bid_on_item>Old Bicycle</bid_on_item>
        <bid_on_item>Racing Bicycle</bid_on_item>
        <bid_on_item>Red Bicycle</bid_on_item>
    </user>
    <user>
        <name>Tom Jones</name>
        <bid_on_item>Motorcycle</bid_on_item>
        <bid_on_item>Tricycle</bid_on_item>
    </user>
</result>

1.5 Use Case "SGML": Standard Generalized Markup Language

1.5.1 Description

The example document and queries in this Use Case were first created for a 1992 conference on Standard Generalized Markup Language (SGML). For our use, the Document Type Definition (DTD) and example document have been translated from SGML to XML.

1.5.2 Document Type Definition (DTD)

This use case is based on an implicit (unnamed) input data set, using the DTD shown below.

 <!NOTATION cgm PUBLIC "Computer Graphics Metafile">
 <!NOTATION ccitt PUBLIC "CCITT group 4 raster">

 <!ENTITY % text "(#PCDATA | emph)*">
 <!ENTITY infoflow SYSTEM "infoflow.ccitt" NDATA ccitt>
 <!ENTITY tagexamp SYSTEM "tagexamp.cgm"   NDATA cgm>

 <!ELEMENT report (title, chapter+)>
 <!ELEMENT title %text;>
 <!ELEMENT chapter (title, intro?, section*)>
 <!ATTLIST chapter
               shorttitle CDATA #IMPLIED>
 <!ELEMENT intro (para | graphic)+>
 <!ELEMENT section (title, intro?, topic*)>
 <!ATTLIST section
               shorttitle CDATA #IMPLIED
               sectid ID #IMPLIED>
 <!ELEMENT topic (title, (para | graphic)+)>
 <!ATTLIST topic
               shorttitle CDATA #IMPLIED
               topicid ID #IMPLIED>
 <!ELEMENT para (#PCDATA | emph | xref)*>
 <!ATTLIST para
               security (u | c | s | ts) "u">
 <!ELEMENT emph %text;>
 <!ELEMENT graphic EMPTY>
 <!ATTLIST graphic
               graphname ENTITY #REQUIRED>
 <!ELEMENT xref EMPTY>
 <!ATTLIST xref
               xrefid IDREF #IMPLIED>

1.5.3 Sample Data

The queries in this use case are based on the following sample data. Line numbers have been added to the data to allow the results of queries to be conveniently specified.

 0: <!DOCTYPE report SYSTEM "report.dtd">
 1: <report>
 2: <title>Getting started with SGML</title>
 3: <chapter>
 4: <title>The business challenge</title>
 5: <intro>
 6: <para>With the ever-changing and growing global market, companies and
 7: large organizations are searching for ways to become more viable and
 8: competitive. Downsizing and other cost-cutting measures demand more
 9: efficient use of corporate resources. One very important resource is
10: an organization's information.</para>
11: <para>As part of the move toward integrated information management,
12: whole industries are developing and implementing standards for
13: exchanging technical information. This report describes how one such
14: standard, the Standard Generalized Markup Language (SGML), works as
15: part of an overall information management strategy.</para>
16: <graphic graphname="infoflow"/></intro></chapter>
17: <chapter>
18: <title>Getting to know SGML</title>
19: <intro>
20: <para>While SGML is a fairly recent technology, the use of
21: <emph>markup</emph> in computer-generated documents has existed for a
22: while.</para></intro>
23: <section shorttitle="What is markup?">
24: <title>What is markup, or everything you always wanted to know about
25: document preparation but were afraid to ask?</title>
26: <intro>
27: <para>Markup is everything in a document that is not content. The
28: traditional meaning of markup is the manual <emph>marking</emph> up
29: of typewritten text to give instructions for a typesetter or
30: compositor about how to fit the text on a page and what typefaces to
31: use. This kind of markup is known as <emph>procedural markup</emph>.</para></intro>
32: <topic topicid="top1">
33: <title>Procedural markup</title>
34: <para>Most electronic publishing systems today use some form of
35: procedural markup. Procedural markup codes are good for one
36: presentation of the information.</para></topic>
37: <topic topicid="top2">
38: <title>Generic markup</title>
39: <para>Generic markup (also known as descriptive markup) describes the
40: <emph>purpose</emph> of the text in a document. A basic concept of
41: generic markup is that the content of a document must be separate from
42: the style. Generic markup allows for multiple presentations of the
43: information.</para></topic>
44: <topic topicid="top3">
45: <title>Drawbacks of procedural markup</title>
46: <para>Industries involved in technical documentation increasingly
47: prefer generic over procedural markup schemes. When a company changes
48: software or hardware systems, enormous data translation tasks arise,
49: often resulting in errors.</para></topic></section>
50: <section shorttitle="What is SGML?">
51: <title>What <emph>is</emph> SGML in the grand scheme of the universe, anyway?</title>
52: <intro>
53: <para>SGML defines a strict markup scheme with a syntax for defining
54: document data elements and an overall framework for marking up
55: documents.</para>
56: <para>SGML can describe and create documents that are not dependent on
57: any hardware, software, formatter, or operating system. Since SGML documents
58: conform to an international standard, they are portable.</para></intro></section>
59: <section shorttitle="How does SGML work?">
60: <title>How is SGML and would you recommend it to your grandmother?</title>
61: <intro>
62: <para>You can break a typical document into three layers: structure,
63: content, and style. SGML works by separating these three aspects and
64: deals mainly with the relationship between structure and content.</para></intro>
65: <topic topicid="top4">
66: <title>Structure</title>
67: <para>At the heart of an SGML application is a file called the DTD, or
68: Document Type Definition. The DTD sets up the structure of a document,
69: much like a database schema describes the types of information it
70: handles.</para>
71: <para>A database schema also defines the relationships between the
72: various types of data. Similarly, a DTD specifies <emph>rules</emph>
73: to help ensure documents have a consistent, logical structure.</para></topic>
74: <topic topicid="top5">
75: <title>Content</title>
76: <para>Content is the information itself. The method for identifying
77: the information and its meaning within this framework is called
78: <emph>tagging</emph>. Tagging must
79: conform to the rules established in the DTD (see <xref xrefid="top4"/>).</para>
80: <graphic graphname="tagexamp"/></topic>
81: <topic topicid="top6">
82: <title>Style</title>
83: <para>SGML does not standardize style or other processing methods for
84: information stored in SGML.</para></topic></section></chapter>
85: <chapter>
86: <title>Resources</title>
87: <section>
88: <title>Conferences, tutorials, and training</title>
89: <intro>
90: <para>The Graphic Communications Association has been
91: instrumental in the development of SGML. GCA provides conferences,
92: tutorials, newsletters, and publication sales for both members and
93: non-members.</para>
94: <para security="c">Exiled members of the former Soviet Union's secret
95: police, the KGB, have infiltrated the upper ranks of the GCA and are
96: planning the Final Revolution as soon as DSSSL is completed.</para>
97: </intro>
98: </section>
99: </chapter>
100:</report>

1.5.4 Queries and Results

1.5.4.1 Q1

Locate all paragraphs in the report (all "para" elements occurring anywhere within the "report" element).

Solution in XQuery:

<result>
  { 
    //report//para 
  }
</result>

Expected Result:

Elements whose start-tags are on lines 6, 11, 20, 27, 34, 39, 46, 53, 56, 62, 67, 71, 76, 83, 90, 94

1.5.4.2 Q2

Locate all paragraph elements in an introduction (all "para" elements directly contained within an "intro" element).

Solution in XQuery:

<result>
  { 
    //intro/para 
  }
</result>

Expected Result:

Elements whose start-tags are on lines 6, 11, 20, 27, 53, 56, 62, 90, 94

1.5.4.3 Q3

Locate all paragraphs in the introduction of a section that is in a chapter that has no introduction (all "para" elements directly contained within an "intro" element directly contained in a "section" element directly contained in a "chapter" element. The "chapter" element must not directly contain an "intro" element).

Solution in XQuery:

<result>
  {
    for $c in //chapter
    where empty($c/intro)
    return $c/section/intro/para
  }
</result>

Expected Result:

Elements whose start-tags are on lines 90, 94

1.5.4.4 Q4

Locate the second paragraph in the third section in the second chapter (the second "para" element occurring in the third "section" element occurring in the second "chapter" element occurring in the "report").

Solution in XQuery:

<result>
  { 
    (((//chapter)[2]//section)[3]//para)[2] 
  }
</result>

Expected Result:

Element whose start-tag is on line 67

1.5.4.5 Q5

Locate all classified paragraphs (all "para" elements whose "security" attribute has the value "c").

Solution in XQuery:

<result>
  { 
    //para[@security = "c"] 
  }
</result>

Expected Result:

Element whose start-tag is on line 94

1.5.4.6 Q6

List the short titles of all sections (the values of the "shorttitle" attributes of all "section" elements, expressing each short title as the value of a new element.)

Solution in XQuery:

<result>
  {
    for $s in //section/@shorttitle
    return <stitle>{ $s }</stitle>
  }
</result>

Expected Result:

Attribute values in start-tags on lines 23, 50, 59

1.5.4.7 Q7

Locate the initial letter of the initial paragraph of all introductions (the first character in the content [character content as well as element content] of the first "para" element contained in an "intro" element).

Solution in XQuery:

<result>
  {
    for $i in //intro/para[1]
    return
        <first_letter>{ substring(string($i), 1, 1) }</first_letter> 
  }
</result>

Expected Result:

Character after start-tag on lines 6, 20, 27, 53, 62, 90

1.5.4.8 Q8a

Locate all sections with a title that has "is SGML" in it (all "section" elements that contain a "title" element that has the consecutive characters "is SGML" in its content). The string can be interrupted by sub-elements.

Solution in XQuery:

<result>
  { 
    //section[contains(string(.//title), "is SGML")] 
  }
</result>

Expected Result:

Elements whose start-tags are on lines 51, 60

1.5.4.9 Q8b

Same as (Q8a), but the string cannot be interrupted by sub-elements.

Solution in XQuery:

<result>
  { 
    //section[contains(.//title/text(), "is SGML")] 
  }
</result>

Expected Result:

Element whose start-tag is on line 60

1.5.4.10 Q9

Locate all the topics referenced by a cross-reference anywhere in the report (all the "topic" elements whose "topicid" attribute value is the same as an "xrefid" attribute value of any "xref" element).

Solution in XQuery:

<result>
  {
    for $id in document("input.xml")//xref/@xrefid
    return //topic[@topicid = $id]
  }
</result>

Expected Result:

Element whose start-tag is on line 65

1.5.4.11 Q10

Locate the closest title preceding the cross-reference ("xref") element whose "xrefid" attribute is "top4" (the "title" element that would be touched last before this "xref" element when touching each element in document order).

Solution in XQuery:

<result>
  {
    let $x := //xref[@xrefid = "top4"],
        $t := //title[. precedes $x]
    return item-at($t, length($t))
  }
</result>

Expected Result:

Given xref on line 79, element whose start-tag is on line 75

1.6 Use Case "TEXT": Full-text Search

1.6.1 Description

This use case is based on company profiles and a set of news documents which contain data for PR, mergers and acquisitions, etc. Given a company, the use case illustrates several different queries for searching text in news documents and different ways of providing query results by matching the information from the company profile and the content of the news items.

In this use case, searches for company names are to be interpreted as word-based searches. The words in a company name may be in any case and may be separated by any kind of white space.

1.6.2 Document Type Definition (DTD)

This use case is based on an implicit (unnamed) input data set based on the following DTDs:

<!ELEMENT company (name, ticker_symbol?, description?,
          business_code, partners?, competitors?)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT ticker_symbol (#PCDATA)>
<!ELEMENT description (#PCDATA)>
<!ELEMENT business_code (#PCDATA)>
<!ELEMENT partners (partner+)>
<!ELEMENT partner (#PCDATA)>
<!ELEMENT competitors (competitor+)>
<!ELEMENT competitor (#PCDATA)>

<!ELEMENT news (news_item*)>
<!ELEMENT news_item (title, content, date, author?, news_agent)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT content (par | figure)+ >
<!ELEMENT date (#PCDATA)>
<!ELEMENT author (#PCDATA)>
<!ELEMENT news_agent (#PCDATA)>
<!ELEMENT par (#PCDATA | quote | footnote)*>
<!ELEMENT quote (#PCDATA)>
<!ELEMENT footnote (#PCDATA)>
<!ELEMENT figure (title, image)>
<!ELEMENT image EMPTY>
<!ATTLIST image
    source  CDATA  #REQUIRED >

1.6.3 Sample Data

The queries in this use case are based on the following sample data.

<?xml version="1.0" encoding="ISO-8859-1"?>
<news>
<news_item>
   <title> Gorilla Corporation acquires YouNameItWeIntegrateIt.com </title>
   <content>
      <par> Today, Gorilla Corporation announced that it will purchase
          YouNameItWeIntegrateIt.com. The shares of
          YouNameItWeIntegrateIt.com dropped $3.00 as a result of this
          announcement.
      </par>

      <par> As a result of this acquisition, the CEO of
          YouNameItWeIntegrateIt.com Bill Smarts resigned. He did not
          announce what he will do next.  Sources close to
          YouNameItWeIntegrateIt.com hint that Bill Smarts might be
          taking a position in Foobar Corporation.
      </par>

      <par>YouNameItWeIntegrateIt.com is a leading systems integrator
          that enables <quote>brick and mortar</quote> companies to
          have a presence on the web.
      </par>

   </content>
   <date>1-20-2000</date>
   <author>Mark Davis</author>
   <news_agent>News Online</news_agent>
</news_item>

<news_item>
   <title>Foobar Corporation releases its new line of Foo products
   today</title>
   <content>
      <par> Foobar Corporation releases the 20.9 version of its Foo
            products.  The new version of Foo products solve known
            performance problems which existed in 20.8 line and
            increases the speed of Foo based products tenfold. It also
            allows wireless clients to be connected to the Foobar
            servers.
      </par>
      <par> The President of Foobar Corporation announced that they
            were proud to release 20.9 version of Foo products and
            they will upgrade existing customers <footnote>where
            service agreements exist</footnote>
            promptly. TheAppCompany Inc. immediately announced that it
            will release the new version of its products to utilize
            the 20.9 architecture within the next three months.
      </par>
      <figure>
          <title>Presidents of Foobar Corporation and TheAppCompany
          Inc. Shake Hands</title> <image source="handshake.jpg"/>
      </figure>
   </content>
   <date>1-20-2000</date>
   <news_agent>Foobar Corporation</news_agent>
</news_item>

<news_item> <title>Foobar Corporation is suing Gorilla Corporation for
   patent infringement </title>
   <content>
      <par> In surprising developments today, Foobar Corporation
         announced that it is suing Gorilla Corporation for patent
         infringement. The patents that were mentioned as part of the
         lawsuit are considered to be the basis of Foobar
         Corporation's <quote>Wireless Foo</quote> line of products.
      </par>
      <par>The tension between Foobar and Gorilla Corporations has
         been increasing ever since the Gorilla Corporation acquired
         more than 40 engineers who have left Foobar Corporation,
         TheAppCompany Inc. and YouNameItWeIntegrateIt.com over the
         past 3 months. The engineers who have left the Foobar
         corporation and its partners were rumored to be working on
         the next generation of server products and applications which
         will directly compete with Foobar's Foo 20.9 servers. Most of
         the engineers have relocated to Hawaii where the Gorilla
         Corporation's server development is located.
      </par>
   </content>
   <date>1-20-2000</date>
   <news_agent>Reliable News Corporation</news_agent>
</news_item>
</news>

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE company SYSTEM "company.dtd">
<company>
   <name>Foobar Corporation</name>
   <ticker_symbol>FOO</ticker_symbol>

   <description>Foobar Corporation is a maker of Foo(TM) and
        Foobar(TM) products and a leading software company with a 300
        Billion dollar revenue in 1999. It is located in Alaska.
   </description>

   <business_code>Software</business_code>
   <partners>
        <partner>YouNameItWeIntegrateIt.com</partner>
        <partner>TheAppCompany Inc.</partner>
   </partners>
   <competitors>
        <competitor>Gorilla Corporation</competitor>
   </competitors>
</company>

1.6.4 Queries and Results

1.6.4.1 Q1

Find all news items where the name "Foobar Corporation" appears in the title.

Solution in XQuery:

//news_item/title[contains(./text(), "Foobar Corporation")]

Expected Results

<title>Foobar Corporation releases its new line of Foo
products today</title>
<title>Foobar Corporation is suing Gorilla Corporation for patent
infringement </title>

1.6.4.2 Q2

Find news items where the Foobar Corporation and one or more of its partners are mentioned in the same paragraph and/or title. List each news item by its title and date.

Solution in XQuery:

let $foobar_partners := //company[name = "Foobar Corporation"]//partner
for $item in //news_item
where 
  some $t in $item//title satisfies 
    (contains($t/text(), "Foobar Corporation") 
    and some $partner in $foobar_partners satisfies 
      contains($t/text(), $partner/text())) 
  or some $par in $item//par satisfies 
   (contains($par/text(), "Foobar Corporation") 
     and some $partner in $foobar_partners satisfies 
       contains($par/text(), $partner/text()))
return
    <news_item>
        { $item/title }
        { $item/date }
    </news_item>

Expected Result:

<news_item>
    <title> Gorilla Corporation acquires YouNameItWeIntegrateIt.com </title>
    <date>1-20-2000</date>
</news_item>
<news_item>
    <title>Foobar Corporation releases its new line of Foo products today</title>
    <date>1-20-2000</date>
</news_item>
<news_item>
    <title>Foobar Corporation is suing Gorilla Corporation for patent
    infringement </title>
    <date>1-20-2000</date>
</news_item>

1.6.4.3 Q3

Find titles of news items where Foobar Corporation and one or more of its partners are mentioned in the same sentence, but none of its competitors are mentioned in the news item. (The "." character designates the end of a sentence.)

Solution in XQuery:

let $foobar_partners := //company[name = "Foobar Corporation"]//partner,
    $foobar_competitors := //company[name = "Foobar Corporation"]//competitor
for $item in //news_item
where some $partner in $foobar_partners satisfies 
  contains_in_same_sentence(string($item/content), "Foobar Corporation", $partner/text()) 
      and not(some $competitor in $foobar_competitors satisfies 
                   contains(string($item/content), $competitor/text()))
return
    $item/title

Expected Result:

<title>Foobar Corporation releases its new line of Foo products today </title>

Note:

contains_in_same_sentence() is a function created on the spot to solve this use case.

1.6.4.4 Q4

Find news items where a company and one of its partners is mentioned in the same news item and the news item is not authored by the company itself.

Solution in XQuery:

for $item in //news_item,
    $c in //company
let $partners := $c//partner
where contains(string($item), $c/name/text()) 
  and some $p in $partners satisfies 
    contains(string($item), $p/text()) and $item/news_agent != $c/name
return
    $item

Expected Results: The expected results are the news item elements with the following titles:

Gorilla Corporation acquires YouNameItWeIntegrateIt.com
Foobar Corporation is suing Gorilla Corporation for patent infringement

1.6.4.5 Q5

For each news item that is relevant to the Gorilla Corporation, create an "item summary" element. The content of the item summary is the content of the title, date, and first paragraph of the news item, separated by periods. A news item is relevant if the name of the company is mentioned anywhere within the content of the news item.

Solution in XQuery:

for $item in //news_item
where contains(string($item/content), "Gorilla Corporation")
return
    <item_summary>
        { $item/title/text() }.
        { $item/date/text() }.
        { string(($item//par)[1]) }
    </item_summary>

Expected Result: (with whitespace reformatted for readability)

<item_summary>
   Gorilla Corporation acquires YouNameItWeIntegrateIt.com. 1-20-2000.
   Today, Gorilla Corporation announced that it will purchase 
   YouNameItWeIntegrateIt.com. The shares of YouNameItWeIntegrateIt.com 
   dropped $3.00 as a result of this announcement.
</item_summary>

<item_summary>
   Foobar Corporation is suing Gorilla Corporation for patent infringement.
   1-20-2000. In surprising developments today, Foobar Corporation announced 
   that it is suing Gorilla Corporation for patent infringement. The patents 
   that were mentioned as part of the lawsuit are considered to be the 
   basis of Foobar Corporation's <quote>Wireless Foo</quote> line of products.
</item_summary>

1.6.4.6 Q6

Find news items where two company names and some form of the word "acquire" appear in the title or in the same sentence in one of the paragraphs. A company name is defined as the content of a <name>, <partner>, or <competitor> element within a <company> element.

Solution in XQuery:

let $companies := distinct-values(//company/name/text() 
       union //company//partner/text() 
       union //company//competitor/text())
for $item in //news_item,
    $item_title in $item/title,
    $item_para in $item//par,
    $c1 in $companies,
    $c2 in $companies
where $c1 != $c2 
  and contains_stems_in_same_sentence($item_title/text(), $c1, $c2, "acquire") 
   or contains_stems_in_same_sentence($item_para/text(), $c1, $c2, "acquire")
return
    distinct-values($item)

Note:

contains_stems_in_same_sentence() is a function created on the spot to solve this use case.

Expected Results: The expected results are the news item elements with the following titles:

Gorilla Corporation acquires YouNameItWeIntegrateIt.com
Foobar Corporation is suing Gorilla Corporation for patent infringement

1.7 Use Case "NS" - Queries Using Namespaces

This use case performs a variety of queries on namespace-qualified names.

1.7.1 Description

This use case is based on a scenario in which a neutral mediator is acting with public auction servers on behalf of clients. The reason for a client to use this imaginary service may be anonymity, better insurance, or the possibility to cover more than one market at a time. The following aspects of namespaces are illustrated by this use case:

Syntactic disambiguation when combining XML data from different sources
Re-use of predefined modules, such as XLinks or XML Schema
Support for global classification schemas, such as the Dublin Core

The sample data consists of two records. The schema used for this data uses W3C XML Schema's schema composition to create a schema from predefined, namespace separated modules, and uses XLink to express references. Each record describes a running auction. It embeds data specific to an auctioneer (e.g. the company's credit rating system) and a taxonomy specific to a particular good (jazz records) in a framework that contains data common to all auctions (e.g. start and end time), using namespaces to distinguish the three vocabularies.

Note that namespace prefixes must be resolved to their Namespace URIs before matching namespace qualified names. It is not sufficient to use the literal prefixes to denote namespaces. Furthermore, there are several possible ways to represent namespace declarations. Therefore, processing must be done on the namespace processed XML Information Set, not on the XML text representation.

1.7.2 Document Type Definition (DTD)

DTDs are not fully compatible with namespaces as they can not express the equality of nodes in the same namespace, but different namespace proxies. In a later version of this paper, an XML Schema should be added here.

This use case is based on an implicit (unnamed) input data set.

1.7.3 Sample Data

<?xml version="1.0" encoding="ISO-8859-1"?>

<ma:AuctionWatchList
    xmlns:ma="http://www.example.com/AuctionWatch"
    xmlns:xlink="http://www.w3.org/1999/xlink"
    xmlns:anyzone="http://www.example.com/auctioneers#anyzone"
    xmlns:eachbay="http://www.example.com/auctioneers#eachbay"
    xmlns:yabadoo="http://www.example.com/auctioneers#yabadoo"
>

<!-- ________________________________________________________________________________ -->

<ma:Auction anyzone:ID="0321K372910">

    <ma:AuctionHomepage
        xlink:type="simple"
        xlink:href="http://www.example.com/item/0321K372910"
    />

    <ma:Schedule>
        <ma:Open    xmlns:dt="http://www.w3.org/2001/XMLSchema"
                dt:type="timeInstant">2000-03-21:07:41:34-05:00</ma:Open>
        <ma:Close    xmlns:dt="http://www.w3.org/2001/XMLSchema"
                dt:type="timeInstant">2000-03-23:07:41:34-05:00</ma:Close>
    </ma:Schedule>
    
    <ma:Price>
        <ma:Start ma:currency="USD">3.00</ma:Start>
        <ma:Current ma:currency="USD">10.00</ma:Current>
        <ma:Number_of_Bids>5</ma:Number_of_Bids>
    </ma:Price>

    <ma:Trading_Partners>
        <ma:High_Bidder>
            <eachbay:ID>RecordsRUs</eachbay:ID>
            <eachbay:PositiveComments>231</eachbay:PositiveComments>
            <eachbay:NeutralComments>2</eachbay:NeutralComments>
            <eachbay:NegativeComments>5</eachbay:NegativeComments>
            <ma:MemberInfoPage
                xlink:type="simple"
                xlink:href="http://auction.eachbay.com/members?get=RecordsRUs"
                xlink:role="ma:MemberInfoPage"
            />            
        </ma:High_Bidder>
        <ma:Seller>
            <anyzone:ID>VintageRecordFreak</anyzone:ID>
            <anyzone:Member_Since>October 1999</anyzone:Member_Since>
            <anyzone:Rating>5</anyzone:Rating>
            <ma:MemberInfoPage
               xlink:type="simple"
               xlink:href="http://auction.anyzone.com/members/VintageRecordFreak"
               xlink:role="ma:MemberInfoPage"
            />
        </ma:Seller>
    </ma:Trading_Partners>

    <ma:Details>
        <record xmlns="http://www.example.org/music/records">
            <artist>Miles Davis</artist>
            <title>In a Silent Way</title>
            <recorded>1969</recorded>
            <label>Columbia Records</label>

            <remark>
                With Miles Davis (trumpet), Herbie Hancock (Electric
                Piano), Chick Corea (Electric Piano), Wayne Shorter
                (Tenor Sax), Josef Zawinul (Electric Piano &amp;
                Organ), John McLaughlin (Guitar), and Tony Williams
                (Drums).  The liner notes were written by Frank Glenn,
                and the record is in fine condition.
            </remark>

        </record>
    </ma:Details>

</ma:Auction>

<!-- ________________________________________________________________________________ -->


<ma:Auction yabadoo:ID="13143816">

    <ma:AuctionHomepage
        xlink:type="simple"
        xlink:href="http://auctions.yabadoo.com/auction/13143816"
    />

    <ma:Schedule>
        <ma:Open    xmlns:dt="http://www.w3.org/2001/XMLSchema"
                dt:type="timeInstant">2000-03-19:17:03:00-04:00</ma:Open>
        <ma:Close    xmlns:dt="http://www.w3.org/2001/XMLSchema"
                dt:type="timeInstant">2000-03-29:17:03:00-04:00</ma:Close>
    </ma:Schedule>
    
    <ma:Price>
        <ma:Start ma:currency="USD">3.00</ma:Start>
        <ma:Current ma:currency="USD">3.00</ma:Current>
        <ma:Number_of_Bids>0</ma:Number_of_Bids>
    </ma:Price>

    <ma:Trading_Partners>
        <ma:High_Bidder>
            <eachbay:ID>VintageRecordFreak</eachbay:ID>
            <eachbay:PositiveComments>232</eachbay:PositiveComments>
            <eachbay:NeutralComments>0</eachbay:NeutralComments>
            <eachbay:NegativeComments>0</eachbay:NegativeComments>
            <ma:MemberInfoPage
                xlink:type="simple"
                xlink:href="http://auction.eachbay.com/showRating/user=VintageRecordFreak"
                xlink:role="ma:MemberInfoPage"
            />            
        </ma:High_Bidder>
        <ma:Seller xmlns:seller="http://www.example.com/auctioneers#eachbay">
            <seller:ID>StarsOn45</seller:ID>
            <seller:PositiveComments>80</seller:PositiveComments>
            <seller:NeutralComments>1</seller:NeutralComments>
            <seller:NegativeComments>2</seller:NegativeComments>
            <ma:MemberInfoPage
                xlink:type="simple"
                xlink:href="http://auction.eachbay.com/showRating/user=StarsOn45"
                xlink:role="ma:MemberInfoPage"
            />            
        </ma:Seller>
    </ma:Trading_Partners>

    <ma:Details>
        <record xmlns="http://www.example.org/music/records">
            <artist>Wynton Marsalis</artist>
            <title>Think of One ...</title>
            <recorded>1983</recorded>
            <label>Columbia Records</label>
            <remark xml:lang="en"> Columbia Records 12" 33-1/3 rpm LP,
                #FC-38641, Stereo. The record is still clean and shiny
                and looks unplayed (looks like NM condition).  The
                cover has very light surface and edge wear.
            </remark>
            <remark xml:lang="de"> Columbia Records 12" 33-1/3 rpm LP,
                #FC-38641, Stereo. Die Platte ist noch immer sauber
                und glänzend und sieht ungespielt aus
                (NM Zustand). Das Cover hat leichte Abnutzungen an
                Oberfläche und Ecken.
            </remark>
        </record>
    </ma:Details>

</ma:Auction>         

</ma:AuctionWatchList>

1.7.4 Queries and Results

1.7.4.1 Q1

List all unique namespaces used in the sample data.

Solution in XQuery:

<Q1>
  {
    for $n in distinct-values(get-namespace-uri(//*))
    return
        <ns>{$n}</ns>
  }
</Q1>

Expected Result:

<Q1>
  <ns>http://www.example.com/AuctionWatch</ns>
  <ns>http://www.w3.org/1999/xlink</ns>
  <ns>http://www.example.com/auctioneers#anyzone</ns>
  <ns>http://www.example.com/auctioneers#eachbay</ns>
  <ns>http://www.example.com/auctioneers#yabadoo</ns>
  <ns>http://www.w3.org/2001/XMLSchema</ns>
  <ns>http://www.example.org/music/records</ns>
</Q1>

1.7.4.2 Q2

Select the title of each record that is for sale.

Solution in XQuery:

namespace music = "http://www.example.org/music/records"

<Q2>
  { 
    //music:title 
  }
</Q2>

Expected Result:

<Q2 xmlns:music="http://www.example.org/music/records">
  <music:title>In a Silent Way</music:title>
  <music:title>Think of One ...</music:title>
</Q2>

1.7.4.3 Q3

Select all elements using datatypes from "XML Schema: Part 2" datatypes.

Solution in XQuery:

namespace dt = "http://www.w3.org/2001/XMLSchema"

<Q3>
  { 
    //*[@dt:*] 
  }
</Q3>

(Finds all nodes that have an attribute whose namespace matches the one specified.)

Expected Result:

<Q3 xmlns:dt="http://www.w3.org/2001/XMLSchema"
        xmlns:ma="http://www.example.com/AuctionWatch"
>
  <ma:Open dt:type="timeInstant">2000-03-21:07:41:34-05:00</ma:Open>
  <ma:Close dt:type="timeInstant">2000-03-23:07:41:34-05:00</ma:Close>
  <ma:Open dt:type="timeInstant">2000-03-19:17:03:00-04:00</ma:Open>
  <ma:Close dt:type="timeInstant">2000-03-29:17:03:00-04:00</ma:Close>
</Q3>

1.7.4.4 Q4

List the target URI's of all XLinks in the document.

Solution in XQuery:

namespace xlink = "http://www.w3.org/1999/xlink"

<Q4>
  {
    for $hr in //@xlink:href
    return <ns>{ $hr }</ns>
  }
</Q4>

(Binds $hr to attribute nodes named href. Concatenating the attribute node to a string extracts its value.)

Expected Result:

<Q4>
  <ns>http://auction.anyzone.com/item/0321K372910</ns>
  <ns>http://auction.eachbay.com/members?get=RecordsRUs</ns>
  <ns>http://auction.anyzone.com/members/VintageRecordFreak</ns>
  <ns>http://auctions.yabadoo.com/auction/13143816</ns>
  <ns>http://auction.eachbay.com/showRating/user=VintageRecordFreak</ns>
  <ns>http://auction.eachbay.com/showRating/user=StarsOn45</ns>
</Q4>

1.7.4.5 Q5

Select all records that have a remark in German.

Solution in XQuery:

namespace music = "http://www.example.org/music/records"

<Q5>
  { 
     //music:record[music:remark/@xml:lang = "de"]
  }
</Q5>

Expected Result:

<Q5 xmlns:music="http://www.example.org/music/records">
<music:record>
    <music:artist>Wynton Marsalis</music:artist>
    <music:title>Think of One ...</music:title>
    <music:recorded>1983</music:recorded>
    <music:label>Columbia Records</music:label>

    <music:remark xml:lang="en"> Columbia Records 12" 33-1/3 rpm LP,
        #FC-38641, Stereo. The record is still clean and shiny and
        looks unplayed (looks like NM condition).  The cover has very
        light surface and edge wear.  
    </music:remark>
    <music:remark xml:lang="de"> Columbia Records 12" 33-1/3 rpm LP,
        #FC-38641, Stereo. Die Platte ist noch immer sauber und
        glänzend und sieht ungespielt aus (NM Zustand). Das Cover hat
        leichte Abnutzungen an Oberfläche und Ecken.  
    </music:remark>
</music:record>
</Q5>

1.7.4.6 Q6

Select the closing time elements of all AnyZone auctions currently monitored.

Solution in XQuery:

namespace ma = "http://www.example.com/AuctionWatch"
namespace anyzone = "http://www.example.com/auctioneers#anyzone"

<Q6>
  { 
    //ma:Auction[@anyzone:ID]/ma:Schedule/ma:Close 
  }
</Q6>

Expected Result:

<Q6 xmlns:dt="http://www.w3.org/2001/XMLSchema"
xmlns:ma="http://www.example.com/AuctionWatch">
  <ma:Close dt:type="timeInstant">2000-03-23:07:41:34-05:00</ma:Close>
</Q6>

1.7.4.7 Q7

Select the homepage of all auctions where both seller and high bidder are registered at the same auctioneer.

Solution in XQuery:

namespace ma = "http://www.example.com/AuctionWatch"

<Q7>
  {
    for $a in //ma:Auction
    let $seller_id := $a/ma:Trading_Partners/ma:Seller/*:ID,
        $buyer_id := $a/ma:Trading_Partners/ma:High_Bidder/*:ID
    where namespace-uri($seller_id) = namespace-uri($buyer_id)
    return
        $a/ma:AuctionHomepage
  }
</Q7>

Note:

The function namespace-uri is not defined in [FandO]. Here, we presume that it returns the namespace URI for the name of an element or attribute.

Expected Result:

<Q7 xmlns:xlink="http://www.w3.org/1999/xlink"
    xmlns:ma="http://www.example.com/AuctionWatch" >
  <ma:AuctionHomepage xlink:type="simple"
                    xlink:href="http://auctions.yabadoo.com/auction/13143816" />
</Q7>

1.7.4.8 Q8

Select all traders (either seller or high bidder) without negative comments

Solution in XQuery:

namespace ma = "http://www.example.com/AuctionWatch"

<Q8>
  {
    (for $s in //ma:Trading_Partners/ma:Seller
     where $s/*:NegativeComments = 0
     return $s)
  union 
    (for $b in //ma:Trading_Partners/ma:High_Bidder
     where $b/*:NegativeComments = 0
     return $b)
  }
</Q8>

Expected Result:

<Q8 xmlns:ma="http://www.example.com/AuctionWatch"
        xmlns:eachbay="http://www.example.com/auctioneers#eachbay"
        xmlns:xlink="http://www.w3.org/1999/xlink" >
<ma:High_Bidder>
  <eachbay:ID>VintageRecordFreak</eachbay:ID>
  <eachbay:PositiveComments>232</eachbay:PositiveComments>
  <eachbay:NeutralComments>0</eachbay:NeutralComments>
  <eachbay:NegativeComments>0</eachbay:NegativeComments>
  <ma:MemberInfoPage xlink:type="simple"
     xlink:href="http://auction.eachbay.com/showRating/user=VintageRecordFreak"
     xlink:role="ma:MemberInfoPage" />
</ma:High_Bidder>
</Q8>

1.8 Use Case "PARTS" - Recursive Parts Explosion

This use case illustrates how a recursive query might be used to construct a hierarchic document of arbitrary depth from flat structures stored in a database.

1.8.1 Description

This use case is based on a "parts explosion" database that contains information about how parts are used in other parts.

The input to the use case is a "flat" document in which each different part is represented by a <part> element with partid and name attributes. Each part may or may not be part of a larger part; if so, the partid of the larger part is contained in a partof attribute. This input document might be derived from a relational database in which each part is represented by a row of a table with partid as primary key and partof as a foreign key referencing partid.

The challenge of this use case is to write a query that converts the "flat" representation of the parts explosion, based on foreign keys, into a hierarchic representation in which part containment is represented by the structure of the document.

1.8.2 Document Type Definitions (DTD)

The input data set uses the following DTD:

<!DOCTYPE partlist [
    <!ELEMENT partlist (part*)>
    <!ELEMENT part EMPTY>
    <!ATTLIST part
          partid  CDATA  #REQUIRED
          partof  CDATA  #IMPLIED
          name    CDATA  #REQUIRED>
]>

Although the partid and partof attributes could have been of type ID and IDREF, respectively, in this schema they are treated as character data, possibly materialized in a straightforward way from a relational database. Each partof attribute matches exactly one partid. Parts having no partof attribute are not contained in any other part.

The output data conforms to the following DTD:

<!DOCTYPE parttree [
    <!ELEMENT parttree (part*)>
    <!ELEMENT part (part*)>
    <!ATTLIST part
          partid  CDATA  #REQUIRED
          name    CDATA  #REQUIRED>
]>

1.8.3 Sample Data

<?xml version="1.0" encoding="ISO-8859-1"?>
<partlist>
  <part partid="0" name="car"/>
  <part partid="1" partof="0" name="engine"/>
  <part partid="2" partof="0" name="door"/>
  <part partid="3" partof="1" name="piston"/>
  <part partid="4" partof="2" name="window"/>
  <part partid="5" partof="2" name="lock"/>
  <part partid="10" name="skateboard"/>
  <part partid="11" partof="10" name="board"/>
  <part partid="12" partof="10" name="wheel"/>
  <part partid="20" name="canoe"/>
</partlist>

1.8.4 Queries and Results

1.8.4.1 Q1

Convert the sample document from "partlist" format to "parttree" format (see DTD section for definitions). In the result document, part containment is represented by containment of one <part> element inside another. Each part that is not part of any other part should appear as a separate top-level element in the output document.

Solution in XQuery:

define function one_level (element $p) returns element
{
    <part partid={ $p/@partid } 
          name={ $p/@name } >
        {
            for $s in document("data/parts-data.xml")//part
            where $s/@partof = $p/@partid
            return one_level($s)
        }
    </part>
}

<parttree>
  {
    for $p in document("data/parts-data.xml")//part[empty(@partof)]
    return one_level($p)
  }
</parttree>

Expected Result:

<parttree>
    <part partid="0" name="car">
        <part partid="1" name="engine">
            <part partid="3" name="piston"/>
        </part>
        <part partid="2" name="door">
            <part partid="4" name="window"/>
            <part partid="5" name="lock"/>
        </part>
    </part>
    <part partid="10" name="skateboard">
        <part partid="11" name="board"/>
        <part partid="12" name="wheel"/>
    </part>
    <part partid="20" name="canoe"/>
</parttree>

1.9 Use Case "REF" - Queries based on References

1.9.1 Description

References are an important aspect of XML. This use case describes a database in which references play a significant role, and contains several representative queries that exploit these references.

Suppose that the file "census.xml" contains an element for each person recorded in a recent census. For each person element, the person's name, job, and spouse (if any) are recorded as attributes. The "spouse" attribute is an IDREF-type attribute that matches the ID-type "name" attribute of the spouse element.

The parent-child relationship among persons is recorded by containment in the element hierarchy. In other words, the element that represents a child is contained within the element that represents the child's father or mother. Due to deaths, divorces, and remarriages, a child might be recorded under either its father or its mother (but not both). For the purposes of this exercise, the term "children of X" includes "children of the spouse of X." For example, if Joe and Martha are spouses, and Joe's element contains an element Sam, and Martha's element contains an element Dave, then Joe's children are considered to be Sam and Dave, and Martha's children are also considered to be Sam and Dave. Each person in the census has zero, one, or two parents.

1.9.2 Document Type Definitions (DTD)

This use case is based on an input document named "census.xml", with the following DTD:

<!DOCTYPE census [
  <!ELEMENT census (person*)>
  <!ELEMENT person (person*)>
  <!ATTLIST person
        name    ID      #REQUIRED
        spouse  IDREF   #IMPLIED
        job     CDATA   #IMPLIED >
]>

1.9.3 Sample Data

The following census data describes two friendly families that have several intermarriages.

<census>
  <person name="Bill" job="Teacher">
    <person name="Joe" job="Painter" spouse="Martha">
      <person name="Sam" job="Nurse">
        <person name="Fred" job="Senator" spouse="Jane">
        </person>
      </person>
      <person name="Karen" job="Doctor" spouse="Steve">
      </person>
    </person>
    <person name="Mary" job="Pilot">
      <person name="Susan" job="Pilot" spouse="Dave">
      </person>
    </person>
  </person>
  <person name="Frank" job="Writer">
    <person name="Martha" job="Programmer" spouse="Joe">
      <person name="Dave" job="Athlete" spouse="Susan">
      </person>
    </person>
    <person name="John" job="Artist">
      <person name="Helen" job="Athlete">
      </person>
      <person name="Steve" job="Accountant" spouse="Karen">
        <person name="Jane" job="Doctor" spouse="Fred">
        </person>
      </person>
    </person>
  </person>
</census>

1.9.4 Queries and Results

1.9.4.1 Q1

Find Martha's spouse.

Solution in XQuery:

<result>
  {
    for $m in document("census.xml")//person[@name = "Martha"]
    return shallow($m/@spouse=>person)
  }
</result>

In the above query, the shallow function returns a copy of the node that is the value of $srcval including all its attributes but not its descendants; the copy has a different identity than the node indicated by the value of $srcval. This function is defined in the [FandO].

Expected Result:

<person name="Joe" job="Painter" spouse="Martha" />

1.9.4.2 Q2

Find Joe's children.

Solution in XQuery:

define function children(element $p) 
{
    shallow($p/person) union shallow($p/@spouse=>person/person)
}

<result>
  {
    for $j in document("census.xml")//person[@name = "Joe"]
    return children($j)
  }
</result>

Expected Result:

<result>
  <person name="Sam" job="Nurse" />
  <person name="Karen" job="Doctor" spouse="Steve" />
  <person name="Dave" job="Athlete" spouse="Susan" />
</result>

1.9.4.3 Q3

Find parents of athletes.

Solution in XQuery:

<result>
  {
    for $p in document("census.xml")//person,
        $s in $p/@spouse=>person
    where $p/person/@job = "Athlete" or $s/person/@job = "Athlete"
    return shallow($p)
  }
</result>

Expected Result:

<result>
  <person name="Joe" job="Painter" spouse="Martha" />
  <person name="Martha" job="Programmer" spouse="Joe" />
  <person name="John" job="Artist" />
</result>

1.9.4.4 Q4

Find people who have the same job as one of their parents.

Solution in XQuery:

<result>
  {
    for $p in document("census.xml")//person,
        $c in $p/person
    where $p/@job = $c/@job or $p/@spouse=>person/@job = $c/@job
    return shallow($c)
  }
</result>

Expected Result:

<result>
  <person name="Susan" job="Pilot" spouse="Dave" />
  <person name="Jane" job="Doctor" spouse="Fred" />
</result>

1.9.4.5 Q5

List names of parents and children who have the same job, and their jobs.

Solution in XQuery:

<result>
    {
        for $p in document("census.xml")//person,
            $c in $p/person[@job = $p/@job]
        return
            <match parent={ $p/@name } child={ $c/@name } job={ $c/@job } />
    }
    {
        for $p in document("census.xml")//person,
            $c in $p/@spouse=>person/person[@job = $p/@job]
        return
            <match parent={ $p/@name } child={ $c/@name } job={ $c/@job } />
    }
</result>

Expected Result:

<result>
  <match parent="Mary" child="Susan" job="Pilot" />
  <match parent="Karen" child="Jane" job="Doctor" />
</result>

1.9.4.6 Q6

Find Bill's grandchildren.

Solution in XQuery:

<result>
  {
    for $b in document("census.xml")//person[@name = "Bill"],
        $c in $b/person | $b/@spouse=>person/person,
        $g in $c/person | $c/@spouse=>person/person
    return shallow($g)
  }
</result>

Expected Result:

<result>
  <person name="Sam" job="Nurse" />
  <person name="Karen" job="Doctor" spouse="Steve" />
  <person name="Susan" job="Pilot" spouse="Dave" />
  <person name="Dave" job="Athlete" spouse="Susan" />
</result>

1.9.4.7 Q7

List name-pairs of grandparents and grandchildren.

Solution in XQuery:

<result>
  {
    for $b in document("census.xml")//person,
        $c in $b/person | $b/@spouse=>person/person,
        $g in $c/person | $c/@spouse=>person/person
    return
        <grandparent name={ $b/@name } grandchild={ $g/@name }/>
  }
</result>

Expected Result:

<result>
  <grandparent name="Bill" grandchild="Sam" />
  <grandparent name="Bill" grandchild="Karen" />
  <grandparent name="Bill" grandchild="Susan" />
  <grandparent name="Bill" grandchild="Dave" />
  <grandparent name="Frank" grandchild="Dave" />
  <grandparent name="Frank" grandchild="Helen" />
  <grandparent name="Frank" grandchild="Steve" />
  <grandparent name="Frank" grandchild="Sam" />
  <grandparent name="Frank" grandchild="Karen" />
  <grandparent name="Joe" grandchild="Fred" />
  <grandparent name="Joe" grandchild="Jane" />
  <grandparent name="Martha" grandchild="Fred" />
  <grandparent name="Martha" grandchild="Jane" />
  <grandparent name="John" grandchild="Jane" />
</result>

1.9.4.8 Q8

Find Dave's parents-in-law (parents of his spouse, if any).

Solution in XQuery:

<result>
  {
    for $s in document("census.xml")//person[@name = "Dave"]/@spouse=>person,
        $sp in $s/.. | $s/../@spouse=>person
    return
        shallow($sp)
  }
</result>

Expected Result:

<result>
  <person name="Mary" job="Pilot" />
</result>

1.9.4.9 Q9

Find people with no children.

Solution in XQuery:

<result>
  {
    for $p in document("census.xml")//person
    where empty(children($p))
    return shallow($p)
  }
</result>

(See Q2 for definition of children function.)

Expected Result:

<result>
  <person name="Fred" job="Senator" spouse="Jane" />
  <person name="Susan" job="Pilot" spouse="Dave" />
  <person name="Dave" job="Athlete" spouse="Susan" />
  <person name="Helen" job="Athlete" />
  <person name="Jane" job="Doctor" spouse="Fred" />
</result>

1.9.4.10 Q10

Find single parents (people with children but no spouse)

Solution in XQuery:

<result>
  {
    for $p in document("census.xml")//person[person]
    where empty($p/@spouse=>person)
    return shallow($p)
  }
</result>

Expected Result:

<result>
  <person name="Bill" job="Teacher" />
  <person name="Sam" job="Nurse" />
  <person name="Mary" job="Pilot" />
  <person name="Frank" job="Writer" />
  <person name="John" job="Artist" />
</result>

1.9.4.11 Q11

List the names of all Joe's descendants. Show each descendant as an element with the descendant's name as content and his or her marital status and number of children as attributes. Sort the descendants in descending order by number of children, and secondarily in alphabetical order by name.

Solution in XQuery:

define function descrip (element $e) returns element
{
    let $kids := $e/* union $e/@spouse=>person/*
    let $mstatus :=  if ($e[@spouse]) then "Yes" else "No"
    return
        <person married={ $mstatus } nkids={ count($kids) }>{ $e/@name/text() }</person>
}

define function descendants (element $e)
{
    if (empty($e/* union $e/@spouse=>person/*))
    then $e
    else $e union descendants($e/* union $e/@spouse=>person/*)
}

descrip(descendants(//person[@name = "Joe"])) sortby(@nkids descending, .)

Expected Result:

<result>
  <descendant married="Yes" kids="1">Karen</descendant>
  <descendant married="No" kids="1">Sam</descendant>
  <descendant married="Yes" kids="0">Dave</descendant>
  <descendant married="Yes" kids="0">Fred</descendant>
  <descendant married="Yes" kids="0">Jane</descendant>
</result>

1.10 Use Case "FNPARM" - Functions and Parameters

This use case explores some of the ways in which functions can be defined and invoked. It is based on examples taken from XML Schema Part 0: Primer , and relies in some cases on type and element definitions that are found in that document (referred to hereafter as the "Schema Primer".) Examples have been taken from the Schema Primer because the XML Query Working Group is committed to supporting queries based on the types and elements that can be defined using XML Schema. Only relevant parts of the type and element definitions are repeated in this use case--additional details can be found in the Schema Primer.

Note:

This use case was originally introduced to propose a design for function signatures. The Working Group has since adopted a design for function signatures, different from the one originally proposed, and the use case has been modified accordingly. A more complete discussion of function signatures may be found in [XQuery]. This section may be modified or removed from future versions of the Use Cases.

In general, this use case uses unqualified names for schema objects (for example, complexType and integer rather than xsd:complexType and xsd:integer). This corresponds to a strategy of using the schema namespace as the default namespace. Obviously, other strategies exist in which namespace prefixes would be used with names of schema objects. Since this use case is not primarily about namespaces, an effort has been made to keep namespace prefixes to a minimum.

This use case consists of several "subcases," each of which introduces a schema fragment and one or more functions that operate on data that conforms to the schema fragment. Each subcase explores a particular aspect of function definition and invocation.

1.10.1 Subcase 1: Type Names vs. Element Names

Section 2.2 of the Schema Primer defines a complex type named USAddress and elements named shipTo and billTo, of type USAddress, that are used in purchase orders. Here are the partial definitions (see Schema Primer for details):

<complexType name="USAddress"> . . .

<element name="shipTo" type="po:USAddress"/>

<element name="billTo" type="po:USAddress"/>

This subcase defines a function that takes a parameter which is an element of type po:USAddress and returns an integer:

define function timezone(element of type po:USAddress $a) returns integer
   { . . . }

Note:

This is a user-defined function.

The following expression computes the difference between the timezones of the shipTo address and the billTo address of the purchase order bound to variable $po1:

timezone($po1/shipTo) - timezone($po1/billTo)

(Note: the static type of each argument is element of type po:USAddress.)

1.10.2 Subcase 2: Types Derived by Extension

Section 4.1 of the Schema Primer defines a complex type named Address and two derived types named USAddress and UKAddress, used in international purchase orders. Here are the partial definitions (see Schema Primer for details):

<complexType name="Address"> . . .

<complexType name="USAddress">
   . . . <extension base="ipo:Address"> . . .

<complexType name="UKAddress">
   . . . <extension base="ipo:Address"> . . .

This subcase defines a function that takes a parameter of type Address and returns a string:

define function streetname(element of type ipo:Address $a) returns string
   { . . . }

Suppose that a product can have two warehouses, one in the USA and one in the UK, represented by subelements with the following declarations:

<element name="USAWarehouse" type="ipo:USAddress"/>

<element name="UKWarehouse" type="ipo:UKAddress"/>

The following expressions use the streetname function to find the streetnames of the two warehouses used by the product bound to $product1:

streetname($product1/USAWarehouse)

streetname($product1/UKWarehouse)

1.10.3 Subcase 3: Types Derived by Restriction

Section 4.4 of the Schema Primer defines a complex type named Items and a derived type named confirmedItems. Here are the partial definitions (see Schema Primer for details):

<complexType name="Items">
   <sequence>
      <element name="item" minOccurs="0" maxOccurs="unbounded"> 
. . .

<complexType name="ConfirmedItems">
   <complexContent>
      <restriction base="ipo:Items">
         <sequence>
            <element name="item" minOccurs="1" maxOccurs="unbounded">
. . .

Motivation for this subcase comes from the following statements in Section 4.4 of the Schema Primer: "An application prepared for the values of the base type would not be surprised by the values of the restricted type." ... "All ConfirmedItems-type elements will also be acceptable as Items-type elements."

This subcase defines a function that takes a parameter of type Items and returns a decimal number:

define function totalPrice(element of type ipo:Items $x) returns decimal
   { sum($x/item/price) }

Suppose that an order element can contain subelements named estimate, of type Items, and final, of type confirmedItems. The following expressions invoke the totalPrice function on these subelements of the order bound to variable $order1:

totalPrice($order1/estimate)

(Note: static type of argument is element of type ipo:Items)

totalPrice($order1/final)

(Note: static type of argument is element of type ConfirmedItems)

1.10.4 Subcase 4: Simulated Polymorphism

Most modern computer languages support some form of polymorphism, in which a function call may result in different behaviors depending on the dynamic type of the argument. Polymorphism is often supported by function overloading, in which several functions are defined that have the same name but different signatures (parameter types). However, function overloading will not be supported in XML Query Version 1. Therefore a different mechanism for simulating polymorphism would be useful. This subcase explores one such mechanism.

The base type Address with derived types USAddress and UKAddress, defined in Section 4.1 of the Schema Primer, are repeated here (modified slightly, and showing only the parts relevant for this example):

<complexType name="Address"> . . .

<complexType name="USAddress">
   . . . <extension base="ipo:Address"> . . .
      . . . <element name="zip" type="string"/> . . .

<complexType name="UKAddress">
   . . . <extension base="ipo:Address"> . . .
      . . . <element name="postcode" type="string"/> . . .

This subcase defines a function whose formal parameter is of type ipo:Address. By the principle of subtype substitution, the function can be invoked with an argument of dynamic type po:USAddress or po:UKAddress. The function branches on the dynamic type of its argument.

define function code(element of type ipo:Address $a) returns string
   {
   typeswitch ($a)
      case element of type ipo:USAddress 
           return (treat as element of type ipo:USAddress($a))/zip/data()
      case element of type ipo:UKAddress 
           return (treat as element of type ipo:UKAddress($a))/postcode/data()
      default return "none"
   }

The behavior of the function call code($addr) depends on the dynamic type of the argument. If $addr is of type ipo:USAddress, the function will return the string content of a zip element. If $addr is of type ipo:UKAddress, the function will return the string content of a postcode element. Otherwise, the function will return the string "none".

1.10.5 Subcase 5: Substitution Groups

Section 4.6 of the Schema Primer defines an element named comment, and two other elements in the same substitution group named shipComment and customerComment. Here are the partial definitions (see Schema Primer for details):

<element name="comment" type="string" />

<element name="shipComment" type="string"
   substitutionGroup="ipo:comment" />
. . .

<element name="customerComment" type="string"
   subtitutionGroup="ipo:comment" />
. . .

This use case defines a function called complaint that determines whether a comment is a complaint, returning a boolean value:

define function complaint(element ipo:comment $c) returns boolean
   { . . . }

The following expressions invoke the complaint function on specific comments that are found in the purchase order bound to variable $po1:

complaint($po1/shipComment[1])

complaint($po1/customerComment[1])

1.10.6 Subcase 6: Collections

This subcase illustrates functions which operate on collections. The functions used take an element named mouse as a parameter. This element is defined by the following schema fragment.

<element name="mouse" type="bio:Mouse"/>

The use case defines two functions: a length function, which operates on one mouse, and an avgWeight function, which operates on a sequence of mice.

define function length(element bio:mouse $m) returns float
   { $m/body + $m/tail }

define function avgWeight(element bio:mouse* $m) returns float
   { avg($m/weight) }

The following function invocations use variable $one_mouse, which is bound to one mouse, and expression $zoo//mouse, which evaluates to a collection of one or more mice.

The following function calls are valid.

length($one_mouse)

avgWeight($one_mouse)
avgWeight($zoo//mouse)

The following call is not valid, because a sequence with more than one node can not be treated as a single node.

length($zoo//mouse)

Note that a single element is treated as a list of length one when passed to a function that expects a list.

1.10.7 Subcase 7: Any Element

Occasionally it is useful to define a function that can be invoked on any element, regardless of its name or type. The following function finds all the red children of any element.

define function redChildren(element $e)
   returns element*
{ 
   $e/*[color = "Red"] 
}

The function redChildren can be invoked on a single element of any type.

redChildren($one_element)

Use Case "R"	Don Chamberlin
Use Case "XMP"	Mary Fernandez, Jerome Simeon, Phil Wadler
Use Case "TREE"	Jonathan Robie
Use Case "PARTS"	Michael Rys
Use Case "NS"	Ingo Macherius
Use Case "REF"	Don Chamberlin
Use Case "TEXT"	Umit Yalcinalp
Use Case "SEQ"	Jonathan Robie
Use Case "SGML"	Paula Angerstein
Use Case "FNPARM"	Don Chamberlin

XML Query Use Cases

W3C Working Draft 20 December 2001

Abstract

Status of this Document

Table of Contents

Appendices

1 Use Cases for XML Queries

1.1 Use Case "XMP": Experiences and Exemplars

1.1.1 Document Type Definitions (DTD)

1.1.2 Sample Data

1.1.3 DTD for Q5

1.1.4 Sample Data for Q5

1.1.5 DTD for Q9

1.1.6 Data for Q9

1.1.7 DTD for Q10

1.1.8 Data for Q10

1.1.9 Queries and Results

1.1.9.1 Q1

1.1.9.2 Q2

1.1.9.3 Q3

1.1.9.4 Q4

1.1.9.5 Q5

1.1.9.6 Q6

1.1.9.7 Q7

1.1.9.8 Q8

1.1.9.9 Q9

1.1.9.10 Q10

1.1.9.11 Q11

1.1.9.12 Q12

1.2 Use Case "TREE": Queries that preserve hierarchy

1.2.1 Description

1.2.2 Document Type Definition (DTD)

1.2.3 Sample Data

1.2.4 Queries and Results

1.2.4.1 Q1

1.2.4.2 Q2

1.2.4.3 Q3

1.2.4.4 Q4

1.2.4.5 Q5

1.2.4.6 Q6

1.3 Use Case "SEQ" - Queries based on Sequence

1.3.1 Description

1.3.2 Document Type Definition (DTD)

1.3.3 Sample Data

1.3.4 Queries and Results

1.3.4.1 Q1

1.3.4.2 Q2

1.3.4.3 Q3

1.3.4.4 Q4

1.3.4.5 Q5

1.4 Use Case "R" - Access to Relational Data

1.4.1 Description

1.4.2 Document Type Definition (DTD)

1.4.3 Sample Data

1.4.4 Queries and Results

1.4.4.1 Q1

1.4.4.2 Q2

1.4.4.3 Q3

1.4.4.4 Q4

1.4.4.5 Q5

1.4.4.6 Q6

1.4.4.7 Q7

1.4.4.8 Q8

1.4.4.9 Q9

1.4.4.10 Q10

1.4.4.11 Q11

1.4.4.12 Q12

1.4.4.13 Q13

1.4.4.14 Q14

1.4.4.15 Q15

1.4.4.16 Q16

1.4.4.17 Q17

1.4.4.18 Q18

1.5 Use Case "SGML": Standard Generalized Markup Language

1.5.1 Description

1.5.2 Document Type Definition (DTD)

1.5.3 Sample Data

1.5.4 Queries and Results

1.5.4.1 Q1

1.5.4.2 Q2