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Use Case Subject Search

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The Wiki page URL should be of the form "Use_Case_Name", where Name is a short name by which we can refer to the use case in discussions. The Wiki page URL can act as a URI identifier for the use case. Subject Search


The person responsible for maintaining the correctness/completeness of this use case. Most obviously, this would be the creator.

Jeff Young

Background and Current Practice

Where this use case takes place in a specific domain, and so requires some prior information to understand, this section is used to describe that domain. As far as possible, please put explanation of the domain in here, to keep the scenario as short as possible. If this scenario is best illustrated by showing how applying technology could replace current existing practice, then this section can be used to describe the current practice. Often, the key to why a use case is important also lies in what problem would occur if it was not achieved, or what problem means it is hard to achieve.

Traditionally, subject heading systems are a way to standardize the names of things, typically concepts, that presumably have literary warrant. Typical library practice is to store them in bibliographic records and represent those records on the Web in HTML where they can be indexed by Web search engines. Here is an example from WorldCat:


Note the "More like this" section on this page where these three "Subjects" are listed:

  • Outer space -- Exploration -- Fiction.
  • Jupiter (Planet) -- Fiction.
  • Life on other planets -- Fiction.

From a library perspective, searching for these named concepts using Google produces disappointing results although some bibliographic ties do show through occasionally:


Two short statements stating (1) what is achieved in the scenario without reference to linked data, and (2) how we use linked data technology to achieve this goal.

  1. Use subject heading systems more effectively for Web discovery and reuse
  2. Use HTTP URIs and OWL to identify and deliver better modeled resources for consolidated use by humans, machines, and semantic agents.

Target Audience

The main audience of your case. For example scholars, the general public, service providers, archivists, computer programs...

Use Case Scenario

The use case scenario itself, described as a story in which actors interact with systems. This section should focus on the user needs in this scenario. Do not mention technical aspects and/or the use of linked data.

A science fiction fan looking for something new to read does a Google search for:


Near the top of the Google search results, they see a REST URI that looks like:

  • Browse subject: Outer space--Exploration--Fiction
  • <http://x-describer.org/concept/Outer+space--Exploration--Fiction/>

In today's reality, this is the top Google hit with a PageRank of 2/10:


The Web document at this URI contains a sparse but useful mix of information that gives the concept named "Outer space -- Fiction" a focused and meaningful identity that ranks well in Google. Back in the use case, the scifi fan clicks on a top-ranked book listed on this page that looks like this:

  • 2010 : odyssey two, by Arthur C Clarke
    • http://x-describer.org/book/1234567/

Again comparing this to today's reality, an HTML representation similar to the OCLC Research "Work Page" prototype should be reasonably effective:

This use case assumes the user is authenticated/authorized in the x-describer.org domain and thus the work page includes a hot-link to an MP3 representation that looks like this:

  • Download this audio book (English 1994) in MP3 format
    • http://x-describer.org/book/1234567/content.mp3

This link acts as a proxy for the authenticated/authorized user to download the appropriate copy of this audio book from their configured OpenURL resolver.

Application of linked data for the given use case

This section describes how linked data technology could be used to support the use case above. Try to focus on linked data on an abstract level, without mentioning concrete applications and/or vocabularies. Hint: Nothing library domain specific.

Preface on URI patterns

The URI examples for x-authority.org and x-describer.org are based on the natural one-to-one-to-many hierarchy implied by "303 URIs forwarding to One Generic Document":

  1. Real World Object
    • http://{domainName}/{className}/{instanceName}
    • http://example.org/person/alice
  2. Generic Document
    • http://{domainName}/{className}/{instanceName}/
    • http://example.org/person/alice/
    • (Note the trailing slash)
  3. Web Document
    • http://{domainName}/{className}/{instanceName}/{operationName}
    • http://example.org/person/alice/default.html
    • http://example.org/person/alice/about.rdf

Subject Heading Domain POV

(I cribbed these subject headings from LCSH, but switched the URIs to be more transparent and generalized in an imaginary x-authority.org domain.)

The first two principles of Linked Data are to:

  1. Use URIs as names for things
  2. Use HTTP URIs so that people can look up those names.

The power of Linked Data comes from the potential of stable, unambiguous, globally-dereferencable, content-negotiable, and last-but-not-least sensible "names for things" that people can understand intuitively. In principle, subject heading systems are sensible "names for things" with potential far beyond library use cases. For the sake of transparency, this use case assumes these names are URL-encoded and appear at the end of an HTTP URI following a '/' or '#' as is commonly done in OWL. Because of the vast number of potential subject headings and the focus on identifying concepts only, this use case assumes '/' is the better choice. For example:

URI Token Substitutions

{domainName} = "x-authority.org"
{className} = "concept"
{instanceName} = "Outer space--Exploration"
{operationName} = "about.html" or "about.rdf"

Example Subject Heading Resources

Linked Data Resource Type URI Behavior
Real World Object (a skos:Concept) http://x-authority.org/concept/Outer+space--Exploration 303 (See Other) redirect to ...]
Generic Document http://x-authority.org/concept/Outer+space--Exploration/ 200 (OK) content-negotiate to...
Web document (application/xhtml+xml, text/html) http://x-authority.org/concept/Outer+space--Exploration/about.html See next row
<h1><a href="http://x-authority.org/concept/">X-Authority.org Subject Heading</a></h1>
<th>preferred label</th>
<td>Outer space--Exploration</td>
<th>alternative label</th>
<td>Exploration of space</td>
<td>Solar system--Exploration</td>
<td>Space exploration (Astronautics)</td>
<td>Space research</td>
Web document (application/rdf+xml) http://x-authority.org/concept/Outer+space--Exploration/about.rdf See next row
  <skos:Concept rdf:about="http://x-authority.org/concept/Outer+space--Exploration">
      <skos:prefLabel>Outer space--Exploration</skos:prefLabel>

      <skos:altLabel>Exploration of space</skos:altLabel>
      <skos:altLabel>Solar system--Exploration</skos:altLabel>
      <skos:altLabel>Space exploration (Astronautics)</skos:altLabel>
      <skos:altLabel>Space research</skos:altLabel>

      <skos:inScheme rdf:resource="http://x-authority.org/concept-scheme/subject-heading" />


There are other ways to model subject heading systems involving opaque URIs and/or identifying skosxl:Labels, but the assumption made in this use case is that the concept of outer space exploration is more useful and stable than the currently preferred literal string "Outer space--Exploration".

Describer Domain POV

Information is invariably about something. The same holds true for "information resources". For example, the book "2010 : odyssey two" is an information resource that is about fictionalized outer space exploration. All information resources are subject to this kind of "is about" analysis, regardless of whether it is located on the Web (i.e. a Web document) and/or outside the Web (e.g. a printed book). In this use case, x-describer.org is responsible for finding information resources of interest to their clientele and associating them with the thing(s) they "are about". The x-describer.org domain could be either an individual or collective organization that uses x-authority.org concept names on the "is about" side of the associations. The goal in this use case is to connect user-based subject heading searches to retrievable-content as efficiently as possible using Linked Data with a focus on human interactions starting with Google.

Subject Heading Resource

URI Token Substitutions

{domainName} = "x-describer.org"
{className} = "concept"
{instanceName} = "Outer space--Exploration"
{operationName} = "default.html", "about.rdf"

Linked Data Example

Linked Data Resource Type URI Behavior
Real World Object (a skos:Concept) http://x-describer.org/concept/Outer+space--Exploration 303 (See Other) redirect to...
Generic Document http://x-describer.org/concept/Outer+space--Exploration/ 200 (OK) content-negotiate to...
Web document (application/rdf+xml) http://x-describer.org/concept/Outer+space--Exploration/about.rdf See next row
<skos:Concept rdf:about="http://x-describer.org/concept/Outer+space--Exploration">
    <owl:sameAs rdf:resource="http://x-authority.org/concept/Outer+space--Exploration" />
      <Book rdf:about="http://x-describer.org/book/1234567" />
      <Book rdf:about="http://x-describer.org/book/2345678" />
Web document (text/html, application/xhtml+xml) http://x-describer.org/concept/Outer+space--Exploration/default.html See next row
<head><title>Outer space--Exploration</title></head>
<h1>Books about "Outer space--Exploration"</h1>
  <a href="http://x-describer.org/book/1234567/">2001 : a space odyssey</a>
    <li><a href="http://x-describer.org/book/1234567/content.pdf">Download this e-book (English 1994) in PDF format</a></li>
    <li><a href="http://x-describer.org/book/1234567/content.mp3">Download this audio book (English 1994) in MP3 format</a></li>
    <li><a href="http://x-describer.org/book/1234567/borrow-local">Reserve this book at Ohio State University</a></li>
    <li><a href="http://x-describer.org/book/1234567/borrow-ill">Borrow this book using inter-library loan</a></li>
  <a href="http://x-describer.org/book/2345678/">2010 : odyssey two</a>
    <li><a href="http://x-describer.org/book/2345678/borrow-local">Reserve this book at Ohio State University</a></li>
    <li><a href="http://x-describer.org/book/2345678/borrow-ill">Borrow this book using inter-library loan</a></li>
<h2>Alternate terms:</h2>
<li>Exploration of space</li>
<li>Solar system--Exploration</li>
<li>Space exploration (Astronautics)</li>
<li>Space research</li>


Some people may be bothered by the fact that I coined an alias URI for the x-authority.org concept in the x-describer.org domain:

Semantically, these resources really are the same skos:Concept (witnessed by owl:sameAs). The difference is in the role of Web documents associated with this concept in the different domains:

In the x-authority.org domain, the Web documents are designed for use by x-describer.org-type clientele. In the x-describer.org domain, though, such concepts are the focal point for discovering books about the concept. If you are worried that this difference in associated Web documents creates problems for owl:sameAs, I would argue you are misunderstanding the potential of Linked Data "Real World Objects".

Resource Consumer POV

Existing Work (optional)

This section is used to refer to existing technologies or approaches which achieve the use case. Hint: Specific approaches in the library domain.

Related Vocabularies (optional)

Here you can list and clarify the use of vocabularies (element sets and value vocabularies) which can be helpful and applied within this context.

Problems and Limitations

This section lists reasons why this scenario is or may be difficult to achieve, including pre-requisites which may not be met, technological obstacles etc. Please explicitly list here the technical challenges made apparent by this use case. This will aid in creating a roadmap to overcome those challenges.

Related Use Cases and Unanticipated Uses (optional)

The scenario above describes a particular case of using linked data.. However, by allowing this scenario to take place, the likely solution allows for other use cases. This section captures unanticipated uses of the same system apparent in the use case scenario.

Use Case Vocabulary Merging

Library Linked Data Dimensions / Topics

The dimensions and topics are used to organize the use cases. At the same time, they might help you to identify additional aspects currently not covered. If appropriate topics and/or dimensions are missing, please specify them here and annotate them by a “*”.

*these items are not in the initial list, suggestion for adding them

References (optional)

This section is used to refer to cited literature and quoted websites.