FullSemanticsEasyKeys

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NEEDS AUDIT

The OWL 2 Full semantics of Easy Keys.

Easy Keys are a "lightweight" alternative to full featured inverse functional data properties (IFDPs). Support for compound keys is provided.

Note: This feature is still under construction and discussion.

Easy Keys

Syntax

Note: The RDF syntax is currently only a suggestion, see [1].

  c owl:hasKey SEQ( p_1 ... p_n ) 

Semantics

Axiomatic triples:

 owl:hasKey rdf:type rdf:Property
 owl:hasKey rdfs:domain owl:Class
 owl:hasKey rdfs:range rdf:List

Main semantic condition:

 IF
   l is a sequence of p_1 ... p_n over R_I
 THEN
     (c,l) ∈ EXT_I(S_I(owl:hasKey))
   IF AND ONLY IF
     c ∈ IOC,
     p_1, ..., p_n ∈ P_I,
     (x,z_1), (y,z_1) ∈ EXT_I(p_1) ∧ ... ∧ (x,z_n), (y,z_n) ∈ EXT_I(p_n) → x = y

Considerations

• Easy Keys allow for the free intermixing of data and object properties, see the Structural Spec. So it is not possible to determine from the position of a property in the list of properties whether it is a data property or not. And this also cannot, in general, be entailed from other axioms. Hence, the only thing which can be entailed is that the properties are object properties, and that all the RHSs of the property assertions are individuals. This means that the basic idea of "data keys" isn't really reflected by the OWL Full semantics for Easy Keys, but this is regrettably not achievable.

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