Using SKOS in practice, with examples from the classification domain Antoine Isaac Aida Slavic UDC Seminar 2009

SKOS Simple Knowledge Organization System SKOS is a model to represent KOSs on in RDF in a simple way Not aimed at fitting everything! Not aimed at replacing existing (non-web) formats! Now an official W3C recommendation

SKOS basis SKOS offers a vocabulary for Concepts and concept schemes Labels Semantic relations Notes

Networking controlled vocabularies in SKOS Matching properties as conceptual relations KOS2 animal human object KOS1 animals cats wildcats

The relevance of networked KOSs Johan Stapel, Koninklijke Bibliotheek, Den Haag

Pointers to SKOS deployments SKOS implementation report www.w3.org/2006/07/SWD/SKOS/reference/20090315/implementation.html Library of Congress Subject Headings lcsh.info RAMEAU subject headings stitch.cs.vu.nl/rameau DDC dewey.info

SKOS conversion example: NBC Dutch Basic Classification 21.50 Sculpture: general 21.51 Techniques and materials

Representing classes as concepts 21.51 Techniques and materials

Relationships between classes 21.50 Sculpture: general 21.51 Techniques and materials

Issues with SKOS representation of classifications Captions and labels Languages Time versions of classes Coordination of classes Auxiliary elements …

Issue 1: notations, captions and labels SKOS enables representing notations And human-readable preferred (or alternative) labels, suited for captions 21.51 Techniques and materials

Different choices for notations? Can notations be SKOS preferred labels? They make sense for users & can be displayed We can represent them as language-neutral labels Several choices!

Issue 2: Multiple languages SKOS concepts can have labels in various languages

Issue 2: Multiple languages On dewey.info: one concept per class & language Several choices!

Issue 2: Multiple languages Introducing an abstract entity that denotes the time/language-independent class In RDF, it is possible to use other models in combination with SKOS… Using Dublin Core's isVersionOf link

Raising difficult issues: what is a "concept"? An artifact used in descriptions, e.g., as subjects used as a cluster for different labels with a similar meaning in semantic relationships with other concepts basis for Knowlegde Organization Systems What qualifies as a concept for DDC? For UDC? Can different choices be done?

Issue 3: Tracking modifications 2 RELIGION. FAITHS 21/28 CHRISTIANITY 21 Natural theology. Theodicy. De Deo 22 The Bible. Holy scripture 23 Dogmatic theology 24 Practical theology 25 Pastoral theology 26 Christian church in general 27 General history of the Christian church 28 Christian churches, sects 29 NON CHRISTIAN RELIGIONS NOW..... 2 RELIGION. FAITHS 21 Prehistoric and primitive religions 22 Religions of the Far East 23 Religions of the Indian subcontinent 24 Buddhism 25 Religions of antiquity 26 Judaism 27 Christianity 28 Islam 29 Modern spiritual movements

Creating representations of the versions Each time-specific version should be a skos:Concept because: They are related to other (versions of) classes Classification act refers to a time-specific version A book on the Bible would be wrongly classified by "22" if "22" is the notation for "Far Eastern Religions"

Representing versions of classes IF WE FOCUS ON NOTATION... 22 Representing versions of classes Using Dublin Core's isReplacedBy link

Notations as a reference

Notations as aggregations Notations can be seen as hubs for time-specific version of classes Using the aggregates link from Object Reuse & Exchange (ORE) initiative

Tracking "Far East religions" in UDC database CLASS ID: 16544 NOTATION: 22 DESCRIPTION:Religions originating in the Far East *REPLACES: 299.5 DESCRIPTION: Religion of Oriental peoples ID: 15999 NOTATION HISTORY [22]: YES OLD DESCRIPTION: Bible There is interesting history information (incl. IDs) in the vocabulary management system!

Concepts across notations "Far East religions" existed before: 299.5 It does not belong to 22 alone There is a more abstract Far East Religion entity its conceptual content may be updated while it keeps its position in the hierarchy it might be moved in the notation hierarchy and retain its conceptual content

Representing concepts across notations

Towards stable abstract concepts? Problem: these "abstract concept" entities are not currently explicit in UDC, there is no ID for them

Two different versioning & aggregation mechanisms at work

Conclusion SKOS is an interoperability enabler There are still issues Different conversions reveal different choices But that's not a new problem, really Standardization often needs best practices & use cases Now, it is easier to publish and compare data As data is (will be) linked, it is even crucial to do it! Interaction between information experts and techies is crucial

Thank you! Questions? Drawing inspiration from Joseph Tennis & Stuart Sutton Michael Panzer Jakob Voss