SKOS COMP34512 Sebastian Brandt (Slides by from Sean Bechhofer) - - PowerPoint PPT Presentation

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?

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A typical index

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http://www.anindexer.com/samples/captive/captive1.html

There is hierarchy Are these subsumptions?

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Non-hierarchal relations!

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http://www.anindexer.com/samples/captive/captive1.html

“Related” terms. Redirect

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Redirect?

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http://www.anindexer.com/samples/captive/captive1.html

Note that this relation is hierarchal!

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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

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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

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Desire Paths

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http://www.flickr.com/photos/bdunnette/6432035825/

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Catalogue Terms/ glossary Thesauri Informal is-a Formal is-a Frames Value Restrictions Expressive Logics

A Spectrum of Representation

• Formal representations are not always the most

appropriate for applications

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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

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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. Difgerent controlled vocabularies used to index and

retrieve objects

• Mappings required between the vocabularies
• Also other possible uses (e.g. navigation)

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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.

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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

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SKOS Model

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Labelling

• Lexical Labels associated with

Concepts – Preferred: one per language – Alternate: variants, – Hidden: mis-spellings

• Labels pairwise disjoint.

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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

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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

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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

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SKOS and OWL

• SKOS and OWL are intended for difgerent (but

related) purposes

• SKOS Concept schemes are not formal ontologies in

the way that, e.g. OWL ontologies are formal

• ntologies.
• 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).

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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.

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Annotation

General

• Labels

– Human readable

• Textual Definitions

– Scope notes

• DC style metadata

– authorship

• Change History
• Provenance information

Application Specific

• Entry points for forms
• Driving User interaction
• Hiding engineering

aspects of the model

• Methodological support

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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

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SKOS and OWL

• SKOS and OWL are intended for difgerent 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

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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/

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