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SKOS - 2007 Open Forum on Metadata Registries - NYC


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An brief introduction to SKOS (Simple Knowledge Organization Systems) and its usage in the NSDL Metadata Registry, with some discussion of current challenges.

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SKOS - 2007 Open Forum on Metadata Registries - NYC

  1. 1. “ Integrating Standards in Practice” 10th Open Forum on Metadata Registries July 9-11, 2007 New York City, NY USA An international conference to share and advance knowledge and experience about standards; the technologies that build upon them, and implementation experiences.  SKOS: Simple Knowledge Organization System Jon Phipps Alistair Miles
  2. 2. What is it? <ul><li>S imple K nowledge O rganisation S ystem(s) </li></ul><ul><li>SKOS is … </li></ul><ul><li>for declaring and publishing taxonomies , thesauri or classification schemes , for use in a distributed, decentralised information system (I.e. a semantic web). </li></ul><ul><li>for describing Concepts and creating relationships between Concepts and Terms </li></ul><ul><li>A practical application of RDF </li></ul><ul><li>the application of library science to the semantic web. </li></ul><ul><ul><li>SKOS provides a formal language for representing controlled, structured vocabularies </li></ul></ul>
  3. 3. SKOS Since Open Forum 2005 … <ul><li>Quick Guide to Publishing a Thesaurus on the Semantic Web </li></ul><ul><ul><li>First Working Draft May 2005 </li></ul></ul><ul><li>SKOS Core Guide & SKOS Core Vocabulary Specification </li></ul><ul><ul><li>Second Working Draft published November 2005 </li></ul></ul><ul><li>SKOS Core is now just plain old SKOS </li></ul><ul><li>W3C Semantic Web Deployment Working Group Kicks Off </li></ul><ul><ul><li>W3C Recommendation Track </li></ul></ul><ul><li>SKOS Use Cases and Requirements </li></ul><ul><ul><li>First Working Draft Published (2007-05-16) </li></ul></ul><ul><li>New SKOS Web Site </li></ul><ul><ul><li> </li></ul></ul>
  4. 4. Features <ul><li>Identifying concepts </li></ul><ul><ul><li>URIs for unambiguous global identity and reference </li></ul></ul><ul><li>Labelling concepts </li></ul><ul><ul><li>e.g. lexical labels, symbolic labels, preferred, alternative, hidden … </li></ul></ul><ul><li>Describing & documenting concepts </li></ul><ul><ul><li>e.g. definition, example, scope note, change note, editorial note … </li></ul></ul><ul><li>Relating concepts </li></ul><ul><ul><li>e.g. broader, narrower, related … </li></ul></ul><ul><li>Grouping concepts </li></ul><ul><ul><li>e.g. concept schemes, support for ‘node labels’ … </li></ul></ul><ul><li>Subject Indexing </li></ul><ul><ul><li>e.g. subject of a document, primary subject … </li></ul></ul><ul><li>Multilingual </li></ul><ul><li>Extensible </li></ul>
  5. 5. Concept <ul><li>Defined as: An abstract idea or notion; a unit of thought. </li></ul><ul><li>I.e. A unit of meaning. </li></ul><ul><li>The fundamental unit of a concept scheme. </li></ul>
  6. 6. Concepts
  7. 7. Concept Scheme <ul><li>Defined as: A set of concepts, optionally including statements about semantic relationships between those concepts. </li></ul><ul><li>A … </li></ul><ul><ul><li>thesaurus </li></ul></ul><ul><ul><li>classification scheme </li></ul></ul><ul><ul><li>taxonomy </li></ul></ul><ul><ul><li>terminology </li></ul></ul><ul><ul><li>subject heading system </li></ul></ul><ul><ul><li>[other type of controlled vocabulary] </li></ul></ul><ul><li>… is a concept scheme. </li></ul>
  8. 8. Lexical Labelling <ul><li>SKOS lexical labelling properties </li></ul><ul><ul><li>A set of properties for associating concepts with lexical representations (i.e. terms) </li></ul></ul><ul><ul><ul><li>prefLabel </li></ul></ul></ul><ul><ul><ul><li>altLabel </li></ul></ul></ul><ul><ul><ul><li>hiddenLabel </li></ul></ul></ul>
  9. 9. Lexical Labelling
  10. 10. Symbolic Labelling <ul><li>SKOS symbolic labelling properties </li></ul><ul><ul><li>A set of properties for associating concepts with symbolic representations (i.e. symbolic ‘names’) </li></ul></ul><ul><ul><ul><li>prefSymbol </li></ul></ul></ul><ul><ul><ul><li>altSymbol </li></ul></ul></ul>
  11. 11. Symbolic Labelling
  12. 12. Semantic Relations <ul><li>SKOS semantic relation properties </li></ul><ul><ul><li>A basic set of properties for asserting relationships of meaning between concepts. </li></ul></ul><ul><ul><ul><li>broader </li></ul></ul></ul><ul><ul><ul><li>narrower </li></ul></ul></ul><ul><ul><ul><li>related </li></ul></ul></ul>
  13. 13. Semantic Relations
  14. 14. Semantic Relations
  15. 15. Documentation Properties <ul><li>SKOS documentation properties </li></ul><ul><ul><li>A set of properties for associating concepts with human-readable documentation. </li></ul></ul><ul><ul><ul><li>changeNote </li></ul></ul></ul><ul><ul><ul><li>definition </li></ul></ul></ul><ul><ul><ul><li>editorialNote </li></ul></ul></ul><ul><ul><ul><li>example </li></ul></ul></ul><ul><ul><ul><li>historyNote </li></ul></ul></ul><ul><ul><ul><li>privateNote </li></ul></ul></ul><ul><ul><ul><li>publicNote </li></ul></ul></ul><ul><ul><ul><li>scopeNote </li></ul></ul></ul>
  16. 16. Documentation Properties
  17. 17. Documentation Properties
  18. 18. Subject Indexing <ul><li>SKOS subject indexing properties </li></ul><ul><ul><li>Set of property extensions to the dc:subject property for asserting relationships between information resources and concepts. </li></ul></ul><ul><ul><ul><li>isPrimarySubjectOf </li></ul></ul></ul><ul><ul><ul><li>primarySubject </li></ul></ul></ul><ul><ul><ul><li>isSubjectOf </li></ul></ul></ul><ul><ul><ul><li>subject </li></ul></ul></ul><ul><ul><ul><li>subjectIndicator </li></ul></ul></ul>
  19. 19. Subject Indexing
  20. 20. Grouping <ul><li>SKOS Grouping Properties </li></ul><ul><ul><li>A set of classes and properties for organizing Concepts </li></ul></ul><ul><ul><li>Classes: </li></ul></ul><ul><ul><ul><li>Collection </li></ul></ul></ul><ul><ul><ul><li>orderedCollection </li></ul></ul></ul><ul><ul><li>Concept Properties: </li></ul></ul><ul><ul><ul><li>member </li></ul></ul></ul><ul><ul><ul><li>memberList </li></ul></ul></ul>
  21. 21. Thesaurus Example <ul><li>Term: Economic cooperation </li></ul><ul><li>Used For: Economic co-operation </li></ul><ul><li>Broader terms: Economic policy </li></ul><ul><li>Narrower terms: Economic integration, European economic cooperation, European industrial cooperation, Industrial cooperation </li></ul><ul><li>Related terms: Interdependence </li></ul><ul><li>Scope Note: Includes cooperative measures in banking, trade, industry etc., between and among countries. </li></ul>From UK Archival Thesaurus …
  22. 22. Thesaurus Example
  23. 23. Thesaurus Example <rdf:RDF xmlns:rdf=&quot;; xmlns:rdfs=&quot;; xmlns:skos=&quot;;> <skos:Concept rdf:about=&quot;;> <skos:prefLabel>Economic cooperation</skos:prefLabel> <skos:altLabel>Economic co-operation</skos:altLabel> <skos:scopeNote>Includes cooperative measures in banking, trade, industry etc., between and among countries.</skos:scopeNote> <skos:broader rdf:resource=&quot;;/> <skos:narrower rdf:resource=&quot;;/> <skos:narrower rdf:resource=&quot;;/> <skos:narrower rdf:resource=&quot;;/> <skos:narrower rdf:resource=&quot;;/> <skos:related rdf:resource=&quot;;/> <skos:inScheme rdf:resource=&quot;;/> </skos:Concept> </rdf:RDF> RDF/XML serialisation …
  24. 24. Flexible <ul><li>‘ Pic’n’mix SKOS with other vocabs, e.g. Dublin Core, RSS, FOAF … </li></ul>
  25. 25. Extensible <ul><li>Extended labelling properties </li></ul><ul><ul><li>e.g. common name, scientific name </li></ul></ul><ul><li>Extended concept types </li></ul><ul><ul><li>e.g. AAT’s fundamental facets </li></ul></ul><ul><li>Extended documentation properties </li></ul><ul><ul><li>e.g. MARC21, DDC </li></ul></ul><ul><li>Extended semantic relation properties </li></ul><ul><ul><li>e.g. broader instantive, broader generic, broader partitive </li></ul></ul><ul><li>Can cope with specialised requirements without compromising interoperability </li></ul>
  26. 26. NSDL Metadata Registry <ul><li>The NSDL Registry is intended to provide a complete vocabulary development and management environment for development of vocabularies . Services are primarily directed at vocabulary owners and include provisions for: </li></ul><ul><li>managing access and editing rights for groups of vocabulary maintainers maintaining individual vocabularies </li></ul><ul><li>import and management of existing vocabularies , with and without existing URIs </li></ul><ul><li>namespace management and maintenance services providing permanent URIs </li></ul><ul><li>registered users to receive notifications of changes to vocabularies to which they have subscribed </li></ul><ul><li>content negotiation for retrieval of registered vocabularies in various formats, currently RDF/XML (rdf), XHTML (html), and XML Schema (xsd) </li></ul><ul><li>content negotiation and resolution services for registered vocabularies in non-registry namespaces (in alpha) </li></ul><ul><li>… </li></ul>
  27. 27. NSDL Metadata Registry <ul><li>… </li></ul><ul><li>controlled concept editing and maintenance using SKOS properties </li></ul><ul><li>controlled insertion of reciprocal relationships between concepts </li></ul><ul><li>controlled mapping of relationships between concepts in different vocabularies . </li></ul><ul><li>Concept property-level change history management </li></ul><ul><li>vocabulary- and concept-level version management (in alpha) </li></ul><ul><li>multilingual vocabulary maintenance </li></ul><ul><li>SKOS validation by user input constraint and validation of imported vocabularies </li></ul><ul><li>search and browse for concepts by label </li></ul>
  28. 28. <ul><li>Description of entire vocabulary as a collection of concepts </li></ul><ul><li>Links to Concepts, History, Versions </li></ul><ul><li>Default status and Language </li></ul><ul><li>URI for the vocabulary itself (includes token) </li></ul><ul><li>Links to Users </li></ul><ul><li>Links to XML schema and RDF encoding </li></ul>NSDL Metadata Registry: Example Concept Scheme registration
  29. 29. NSDL Metadata Registry: Example Concept registration <ul><li>Required Preferred Label </li></ul><ul><li>Multi-language support </li></ul><ul><li>Permanent URI for the Concept </li></ul><ul><li>Support for status </li></ul><ul><li>Links to other Concept properties </li></ul><ul><li>Link to RDF fragment </li></ul>
  30. 30. NSDL Metadata Registry: Example Concept Property editing <ul><li>Guided selection of Concept properties </li></ul>
  31. 31. NSDL Metadata Registry: Example Concept Property editing <ul><li>Guided selection of Concept properties </li></ul><ul><li>Guided selection of related concept when using a “relationship” property </li></ul>
  32. 32. NSDL Metadata Registry: Example Concept Property editing <ul><li>Guided selection of Concept properties </li></ul><ul><li>Guided selection of related concept when using a “relationship” property </li></ul><ul><li>Support for property-level status </li></ul><ul><li>Links to other Concept properties </li></ul>
  33. 33. NSDL Metadata Registry: User Management <ul><li>Users and rights can be associated with specific Vocabularies </li></ul><ul><li>Vocabulary admins can assign Users and editorial rights </li></ul><ul><li>Any user who creates a new Vocabulary is automatically the admin for it </li></ul>
  34. 34. NSDL Metadata Registry: HTTP Publishing <ul><li>Implements http content negotiation (W3C ‘Cookbook’) based on W3C TAG httpRange-14 for document retrieval </li></ul><ul><ul><li>See the Recipes and </li></ul></ul><ul><li>We use ‘slash’ (/) URIs instead of ‘hash’ (#) </li></ul><ul><ul><li>Hash URIs must return the entire document when any fragment (identified by #) is requested </li></ul></ul><ul><ul><li>We think this is impractical for information resources </li></ul></ul>
  35. 35. NSDL Metadata Registry: HTTP Publishing <ul><li>Also implements ‘extension’-based document retrieval… </li></ul><ul><ul><li>A request for a document of the type ‘application/rdf+xml’ located at… http:// </li></ul></ul><ul><ul><li>redirects to… </li></ul></ul><ul><ul><li>Which returns… </li></ul></ul>
  36. 36. NSDL Metadata Registry: Versioning <ul><li>Time-slice versioning </li></ul><ul><ul><li>Saves the state of the Scheme whenever a Concept property is added or changed </li></ul></ul><ul><li>RESTful interface </li></ul><ul><ul><li>Scheme or Concept state can be retrieved by appending an encoded UTC Timestamp to URI… </li></ul></ul><ul><ul><li>e.g. scheme current trunk </li></ul></ul><ul><ul><li>e.g. scheme as of “2007-01-26T01:15:38.000Z” </li></ul></ul><ul><li>Only Concept properties that have ‘Published’ state </li></ul><ul><li>Provides a permanent URI for Scheme/Concept at any given point in time -- helps minimize ‘version churn’ </li></ul>
  37. 37. NSDL Metadata Registry: Versioning <ul><li>Named versions </li></ul><ul><ul><li>Identifies an ‘official’ version by naming a time-slice </li></ul></ul><ul><ul><li>Vocabulary admin may apply a version name to any time-slice in the past </li></ul></ul><ul><li>RESTful interface </li></ul><ul><ul><li>Scheme or Concept state can be retrieved by appending a version to URI… </li></ul></ul><ul><ul><li>e.g. scheme as of “2007-01-26T01:15:38.000Z” permanently named “Release Version 1.2” </li></ul></ul><ul><li>Currently no support for editable branches </li></ul>
  38. 38. SWDWG <ul><li>Semantic Web Deployment Working Group </li></ul><ul><ul><li> </li></ul></ul><ul><li>Began: 10 October 2006 </li></ul><ul><li>Lifetime: 20 months </li></ul><ul><li>Chairs: </li></ul><ul><ul><li>Guus Schreiber </li></ul></ul><ul><ul><li>Thomas Baker </li></ul></ul>
  39. 39. SWDWG: SKOS <ul><li>Deliverables and Schedule </li></ul><ul><ul><li> </li></ul></ul><ul><ul><li>SKOS Use Cases and Requirements </li></ul></ul><ul><ul><li>SKOS Test Cases </li></ul></ul><ul><ul><li>SKOS Semantics (Normative Specification) </li></ul></ul><ul><ul><li>SKOS Primer </li></ul></ul><ul><ul><li>SKOS Vocabulary Overview </li></ul></ul><ul><li>March 2008: SKOS Proposed Recommendation </li></ul>
  40. 40. SWDWG: SKOS <ul><li>Use Cases & Requirements Analysis </li></ul><ul><ul><li>Public Working Draft (May 2007) </li></ul></ul><ul><ul><li>Do you have a use case or requirements/issues for SKOS? </li></ul></ul><ul><ul><li>We’d still like to know… mailto:// </li></ul></ul>
  41. 41. SWDWG: SKOS Current Use Cases <ul><li>Dutch and French national libraries -- an integrated view to medieval illuminated manuscripts </li></ul><ul><li>Bio-zen ontology framework for representing scientific discourse in life science </li></ul><ul><li>The FAO AIMS project – a semantic search service across mapped multilingual thesauri in the agriculture domain </li></ul><ul><li>BAE Systems -- The Product Life Cycle Support (PLCS) application </li></ul><ul><li>CHOICE@CATCH ranking of candidate terms for description of radio and TV programs </li></ul><ul><li>BIRNLex: a lexicon for neurosciences </li></ul><ul><li>Radlex: a lexicon for radiology </li></ul><ul><li>NSDL Metadata Registry </li></ul>
  42. 42. SWDWG: SKOS Selected Open Issues <ul><li>Typed relationships between labels </li></ul><ul><ul><li>SKOS allows the expression of semantic relationships (broader, related) between concepts. </li></ul></ul><ul><ul><li>It also allows relationships between concepts and labels (prefLabel, altLabel). </li></ul></ul><ul><li>Issue: </li></ul><ul><ul><li>There is nothing in SKOS to capture links between labels themselves. </li></ul></ul>
  43. 43. SWDWG: SKOS Selected Open Issues <ul><li>Basic Label Semantics Issues </li></ul><ul><ul><li>Can a resource have two “preferred labels”? </li></ul></ul><ul><ul><li>Can a label be both &quot;preferred&quot; and “alternative? for the same resource? </li></ul></ul><ul><ul><li>If a label is “hidden”, can it also be “preferred” or “alternative” for the same resource? </li></ul></ul>
  44. 44. SWDWG: SKOS Selected Open Issues <ul><li>Grouping in Concept Hierarchies </li></ul><ul><ul><li>Thesaurus standards describe the use of “node labels” for convenient grouping and display. </li></ul></ul><ul><li>Issue: </li></ul><ul><ul><li>The current grouping support in SKOS (called “Collections”) introduces logical inconsistencies into the SKOS spec. </li></ul></ul><ul><ul><li>this is bad </li></ul></ul><ul><li>And more than a few others… </li></ul>
  45. 45. SWDWG: SKOS <ul><li>So we’ve definitely got issues! </li></ul><ul><ul><li> </li></ul></ul><ul><li>A final word from Alistair Miles… </li></ul><ul><li>“ Bring out the unsolved stuff, don't hide any of the difficulties.” </li></ul><ul><li>“ N.B. interoperability with ISO11179 is a requirement and a big issue for SKOS, so let everybody know we're going to need help there.” </li></ul><ul><li>“ Take home message: lots of interesting challenges and issues, really want to hear from registry community!” </li></ul>
  46. 46. Links <ul><li>SKOS Homepage </li></ul><ul><ul><li> </li></ul></ul><ul><li>SKOS Guide </li></ul><ul><ul><li> </li></ul></ul><ul><li>SKOS Vocabulary Specification </li></ul><ul><ul><li> </li></ul></ul><ul><li>SWD-WG Home Page </li></ul><ul><ul><li> </li></ul></ul><ul><li>SWD-WG Mailing list </li></ul><ul><ul><li> </li></ul></ul><ul><ul><li> </li></ul></ul><ul><li>NSDL Metadata Registry </li></ul><ul><ul><li> </li></ul></ul><ul><ul><li>Please play in our sandbox! </li></ul></ul><ul><ul><li> </li></ul></ul><ul><li>The Registry blog (gotta have one) </li></ul><ul><ul><li> </li></ul></ul><ul><li>Jon Phipps </li></ul><ul><ul><li> </li></ul></ul><ul><ul><li>Thanks for listening  </li></ul></ul>