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Rather than providing a direct semantics, the semantics of WSML is de-
fined through several mappings to well-known formalisms in order not only to
facilitate understanding of the language, but also so that complexity results
follow immediately from known definitions and the accepted literature. To
give an idea of the semantics, 4 we show the example ontology booksOntology
(Listing 7.1), transformed into F-Logic programming:
← x [ y ⇒z ] ∧ w [ y →v ] not v : z
book [ title ⇒ string ]
book [ hasAuthor ⇒author ]
author :: person
author [ authorOf ⇒book ]
y [ hasAuthor →x ] ← x : author ∧ x [ authorOf →y ]
y [ authorOf →x ] ← y : author ∧ x [ hasAuthor →y ]
cart [ id ⇒ string ]
book [ hasAuthor ⇒author ]
← x : cart ∧ not x [ id →y ]
← x : cart ∧ x [ id →y ] ∧ x [ id →z ] ∧ y = z
cart [ items ⇒amazonBook ]
crimeAndP unishment : book
crimeAndP unishment [ title → CrimeandP unishment ”]
crimeAndP unishment [ hasAuthor →dostoyevsky ]
x : author ← authorShip ( x, y )
y : document ← authorShip ( x, y )
authorship ( x, y ) ← x [ authorOf →y ] ∧ x : author
Note that in this example, a rule without a head is an integrity constraint.
A model of the rule base violates an integrity constraint if the body of the
constraint is true in the model. We call a transformed WSML-Flight ontology
O satisfiable iff the transformed rule base π ( O ) (without the constraints) has
a perfect model M O [72, Appendix A] and this model does not violate any of
the integrity constraints. Furthermore, a satisfiable WSML-Flight ontology O
entails a ground formula F iff π ( F )istruein M O .
7.4 WSML Exchange Syntaxes
For exchange over the Web and interoperation with RDF-based applications,
WSMLdefinesanXMLsyntaxandanRDFsyntax.
7.4.1 The WSML XML Syntax
The Extensible Markup Language (XML) 5 is a markup language for inter-
change of structured and semistructured data over the Web. WSML specifies
a serialization in XML for exchange of WSML specifications over the Web.
The WSML XML syntax is similar to the human-readable syntax, both
in keywords and in structure. We have defined the XML syntax through
4 Space limitations prevent us from giving the complete semantics of WSML. In-
stead, we have given a rough sketch of the WSML semantics and refer the inter-
ested reader to [30].
5 http://www.w3.org/XML .
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