SKOS COMP34512 Sebastian Brandt (Slides by from Sean Bechhofer) brandt@cs.manchester.ac.uk sean.bechhofer@manchester.ac.uk Friday, 2 May 2014
Terminology Management • Consider our original use case – Building an index for a children’s book on animals – Target: Hierarchical controlled vocabulary • I.e., a taxonomy • We used an ontology as the development KR – Terms mapped to classes – The hierarchical relations were mapped to subsumption – The fully classified class graph == the taxonomy • Is this representationally adequate – For all controlled vocabularies? – For our index? 2 Friday, 2 May 2014
A typical index There is hierarchy Are these subsumptions? 3 http://www.anindexer.com/samples/captive/captive1.html Friday, 2 May 2014
Non-hierarchal relations! “Related” terms. Redirect 4 http://www.anindexer.com/samples/captive/captive1.html Friday, 2 May 2014
Redirect? Not e that this relation is hierarchal! 5 http://www.anindexer.com/samples/captive/captive1.html Friday, 2 May 2014
Terminology Management • Not all terminologies are the same! – Data oriented • Intended to feed into databases • Intended to support statistical analysis • Logic seems to do rather well there – Linguistically oriented • Mapping linguistic relations (WordNet) • Not very logical! – E.g., terms have multiple senses – Navigationally oriented • E.g., the Dewey decimal system • Cognitively salient relations • Many terminologies serve multiple purposes 6 Friday, 2 May 2014
Navigation vs. Subsumption • Subsumption – Based on the way the world is/model theoretic – Strict inclusion – Amenable to a logical treatment • In particular, derivable from features of relational structures • Navigation – Based on “how we think” – Associative • Associations may be “hierarchal” (in some sense) or not – Generally “brute,” vague, & informal • Derivable from patterns of behavior (sometimes) • Cognitive cow paths 7 Friday, 2 May 2014
Desire Paths http://www.flickr.com/photos/bdunnette/6432035825/ 8 Friday, 2 May 2014
A Spectrum of Representation Formal Value is-a Restrictions Thesauri Catalogue Expressive Terms/ Informal Frames Logics glossary is-a • Formal representations are not always the most appropriate for applications 9 Friday, 2 May 2014
SKOS • SKOS : Simple Knowledge Organisation Scheme • Used to represent term lists, controlled vocabularies and thesauri • Lexical labelling • Simple broader/narrower hierarchies, no formal semantics • W3C Recommendation 10 Friday, 2 May 2014
Primary Use Cases/Scenarios A. Single controlled vocabulary used to index and then retrieve objects • Query/retrieval may make use of some structure in the vocabulary B. Di fg erent controlled vocabularies used to index and retrieve objects Mappings required between the vocabularies • • Also other possible uses (e.g. navigation) 11 Friday, 2 May 2014
SKOS Goals • to provide a simple , machine-understandable , representation framework for Knowledge Organisation Systems (KOS)… • that has the flexibility and extensibility to cope with the variation found in KOS idioms… • that is fully capable of supporting the publication and use of KOS within a decentralised , distributed , information environment such as the world wide (semantic) web. 12 Friday, 2 May 2014
Concept Schemes • A concept scheme is a set of concepts, potentially including statements about relationships between those concepts – Semantic Relationships • Broader/Narrower Terms • Related Terms – Lexical Labels • Preferred, alternative and hidden labels – Additional documentation • Notes, comments, descriptions 13 Friday, 2 May 2014
SKOS Model Friday, 2 May 2014
Labelling • Lexical Labels associated with Concepts – Preferred: one per language – Alternate: variants, – Hidden: mis-spellings • Labels pairwise disjoint. Friday, 2 May 2014
Semantic Relations • Hierarchical and Associative • Broader/Narrower • Loose (i.e. no) semantics – A publishing vehicle, not a set of thesaurus construction guidelines • broader/narrower not (inherently) transitive in SKOS Friday, 2 May 2014
Not (necessarily?!) transitive? • But, surely – if A is broader than B – and B is broader than C – that A is broader than C! – i.e., TRANSITIVE!? • Consider the Library of Congress Subject Organization – Vehicles broader than • Cars broader than – Wheels – Is “Vehicles” necessarily broader than “Wheels”? • (Not all wheels are vehicular...spinning wheels, potter’s wheels) • We might “fix” this by implicitly making the Wheels, “car wheels” • Definitely not subsumptions all the way! – Vehicle to Cars, yes – Cars to Wheels is partonomic 17 Friday, 2 May 2014
Mapping Relations Subproperties of Semantic Relations • Intended for cross-scheme usage • • Although no formal enforcement • Usually there’s bespoke management code • Or things are passed to the user • exactMatch similar to EquivalentClasses • But again! Transitivity fail • or transitivity “caution” • broad- and narrowMatch • “like” subsumption Much more similar to “see” • – or “see also” – The relationship isn’t reliable • In the sense of having a semantics Friday, 2 May 2014
SKOS and OWL • SKOS and OWL are intended for di fg erent (but related) purposes • SKOS Concept schemes are not formal ontologies in the way that, e.g. OWL ontologies are formal ontologies. • There is no formal semantics given for the conceptual hierarchies (broader/narrower) represented in SKOS. • Contrast with OWL subclass hierarchies which have a formal interpretation (in terms of sets of instances). 19 Friday, 2 May 2014
SKOS and OWL • SKOS Concepts not intended for instantiation in the same way that OWL Classes are instantiated – Leo is an instance of Lion – Born Free is a book about Lions • Concept Schemes allow us to capture general statements about things that aren’t necessarily strictly true of everything – It’s useful to be able to navigate from Cell to Nucleus, even though it’s not the case that all Cells have a Nucleus – Relationships between Polio and Polio virus, Polio vaccine, Polio disease… – Relationships between Accident and Accident Prevention, Accidents in the Home, Radiation Accidents… • But we can’t necessarily draw the same kinds of inferences about SKOS hierarchies. – Broader hierarchy is not transitive. • Although mechanisms are available which allow us to query the transitive closure of the hierarchy. 20 Friday, 2 May 2014
Annotation General Application Specific • Labels • Entry points for forms – Human readable • Driving User interaction • Textual Definitions • Hiding engineering – Scope notes aspects of the model • DC style metadata • Methodological support – authorship • Change History • Provenance information 21 Friday, 2 May 2014
SKOS as Annotation • SKOS labelling and documentation properties are defined as OWL Annotation Properties – Preferred/Alternate/Hidden Labels – Documentation/Notes • SKOS then provides a standardised vocabulary for annotating OWL ontologies • Leverage existing tooling. – OWL API – Protégé 22 Friday, 2 May 2014
SKOS and OWL • SKOS and OWL are intended for di fg erent purposes. • OWL allows the explicit modelling/description of a domain • SKOS provides vocabulary and navigational structure • Annotation mechanisms allow them to coexist – And even interact – A key modelling technique is exploiting OWL knowledge to support SKOS relations 23 Friday, 2 May 2014
Resources • SKOS: – http://www.w3.org/TR/skos-reference/ – http://www.w3.org/TR/skos-ucr/ – http://www.w3.org/TR/2009/NOTE-skos- primer-20090818/ 24 Friday, 2 May 2014
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