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This section last edited on DateTime() is part of the ["SKOS/Semantics"] wiki draft.


@@TODO general introduction

Basis for the Semantics

In this document, semantic conditions on the interpretation of the SKOS Vocabulary may be given in one of two forms:

This formulation of the SKOS semantics has been designed to allow applications to choose whether to view SKOS as a vocabulary extension of either RDF, RDFS or OWL Full.

Note that some aspects of the semantics of SKOS, which are deemed to be useful under certain circumstances, cannot be stated without violating the syntactic constraints imposed by the OWL DL language. This has been raised as an [ issue] for the SWDWG, which has yet to be resolved.

As a temporary solution, this document marks a number of axiomatic triples as [OWL-Full]. Applications MAY then choose to view SKOS as a vocabulary extension of OWL DL, by ignoring any triples marked as such.

Guidance on how to use the SKOS Vocabulary within the constraints of the OWL DL language will be given in the ["SKOS/Primer"].

URI Abbreviations

Throughout this document, URIs are presented in an abbreviated form, using the following table of abbreviations:

URI Abbreviation Table




Structure of this Document

The main body of this document is divided into a number of different "modules". This is entirely for the convenience of the reader, and no formal meaning is intended by the word "module".

The structure of each module is decribed below.

First, URIs from the SKOS Vocabulary are given, to which subsequent statements within the module apply. These are given as a list of abbreviated URIs, using abbreviations set out in section @@TODO. For example:


ex:foo ex:bar

Second, semantic conditions on the interpretation of these elements are stated. As described in section @@TODO above, semantic conditions are either stated as a set of RDF triples using the same syntax as is used in [RDF Semantics] (i.e. N-Triples with URI abbreviations allowed), for example:

Axiomatic Triples

ex:foo rdfs:range rdfs:Literal. BR ex:bar rdfs:range rdfs:Literal. BR ex:foo rdfs:subPropertyOf rdfs:label. [OWL-Full] BR ex:bar rdfs:subPropertyOf rdfs:label. [OWL-Full]

or as formal statements following the conventions and definitions established in section 5 of [OWL Semantics], for example:

Semantic Conditions

If <x,y> is in EXTI(SI(ex:foo)) then there exists some z such that <x,z> is in EXTI(SI(ex:bar)).

Third, informative examples may be given using the [Turtle] RDF syntax, which are consistent with the semantics, for example:

ex:a ex:foo "bar"@en.

Fourth, if applicable, informative examples may be given using the [Turtle] RDF syntax, which are not consistent with the semantics (i.e. give rise to a logical contradiction).

Fifth, any syntactic conditions which apply to the use of the vocabulary in RDF graphs are stated, using keywords MUST, SHOULD, MAY etc. as defined by [ [RFC 2199]], for example:

Syntactic Conditions

An application MAY ignore any triple in an RDF graph where the predicate is either ex:foo or ex:bar and the object is NOT a plain literal.

Finally, any new entailment rules are stated, which follow from the semantic conditions given in the module. These rules are informative only, and are presented using the same conventions as used in section @@TODO of [RDF Semantics]. For example:

Entailment Rules (Informative)

If E contains

then add

uuu ex:foo xxx .

uuu ex:bar _:nnn .BR where _:nnn identifies a new blank node in the graph.

SKOS/Semantics/Introduction (last edited 2007-07-24 15:51:17 by RalphSwick)