XML Query Use Cases -- Review Version

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 [XQuery Requirements] document, without solutions in concrete query languages. Now it is being republished with solutions for [XQuery]. These use cases are also being used by the W3C XML Query Testing Task Force.

The input environment for each use case is stated in its Document Type Definition (DTD) section. All of these use cases assume that input is provided in the form of one or more documents with specific names. For instance, the authors in a document may be accessed with expressions like this:

doc("http://bstore1.example.com/bib.xml")//author

Some implementations of XQuery bind input to external variables. If the environment has bound the external variable $b to the same document used in the above query, this expression would return the same set of authors:

$b//author

Some implementations of XQuery predefine a single 'context item', which is available at the root level of a query, and which is used to resolve paths that begin with a leading slash. In such an implementation, if the context item is bound to document node of the same well-formed document used in the previous examples, this expression would return the same set of authors:

//author

Previous versions of this document accessed implicit documents using the input() function, which no longer exists. The input() function had similar functionality to a predefined context item, except that it could be bound to a sequence of nodes, whereas the context item may only be bound to a single node. The use cases that used input() have been rewritten to use explicit file names.

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].

To make output more readable, the output of queries has been formatted using whitespace which may not be returned by a query processor. This whitespace should not be considered normative for the correctness of results.

These queries weretested with a dynamicimplementation of XQuery. Somequeries may require additional type declarations to be usedwith animplementation that implements the Static Typing feature.

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://bstore1.example.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 "bstore1.example.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://bstore2.example.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://bstore2.example.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>bstore2.example.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title>Advanced Programming in the Unix environment</title>
        <source>bstore1.example.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title>TCP/IP Illustrated</title>
        <source>bstore2.example.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title>TCP/IP Illustrated</title>
        <source>bstore1.example.com</source>
        <price>65.95</price>
    </book>
    <book>
        <title>Data on the Web</title>
        <source>bstore2.example.com</source>
        <price>34.95</price>
    </book>
    <book>
        <title>Data on the Web</title>
        <source>bstore1.example.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.

Editorial note
This solution was provided by Michael Wenger, a student at the University of Würzburg.

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

ITEMNO	DESCRIPTION	OFFERED_BY	START_DATE	END_DATE	RESERVE_PRICE
1001	Red Bicycle	U01	1999-01-05	1999-01-20	40
1002	Motorcycle	U02	1999-02-11	1999-03-15	500
1003	Old Bicycle	U02	1999-01-10	1999-02-20	25
1004	Tricycle	U01	1999-02-25	1999-03-08	15
1005	Tennis Racket	U03	1999-03-19	1999-04-30	20
1006	Helicopter	U03	1999-05-05	1999-05-25	50000
1007	Racing Bicycle	U04	1999-01-20	1999-02-20	200
1008	Broken Bicycle	U01	1999-02-05	1999-03-06	25

USERID	ITEMNO	BID	BID_DATE
U02	1001	35	1999-01-07
U04	1001	40	1999-01-08
U02	1001	45	1999-01-11
U04	1001	50	1999-01-13
U02	1001	55	1999-01-15
U01	1002	400	1999-02-14
U02	1002	600	1999-02-16
U03	1002	800	1999-02-17
U04	1002	1000	1999-02-25
U02	1002	1200	1999-03-02
U04	1003	15	1999-01-22
U05	1003	20	1999-02-03
U01	1004	40	1999-03-05
U03	1007	175	1999-01-25
U05	1007	200	1999-02-08
U04	1007	225	1999-02-12

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 "STRING"	Umit Yalcinalp
Use Case "SEQ"	Jonathan Robie
Use Case "SGML"	Paula Angerstein
Use Case "STRONG"	Jonathan Robie and Phil Wadler. Schemas and data taken from [XMLSchema0] .