WSML – a Language for WSMO - Enabling Semantic Web Services: The Web Service Modeling Ontology - page 79

description of Semantic Web services and ontologies. Section 7.7 contains a
summary of the Chapter and outlines future work which is planned for WSML.
The WSML specification and related documents can be found on line at
http://www.wsmo.org/wsml/wsml-syntax .

7.1 The WSML Layering

Figure 7.1a shows the different variants of WSML and the relationships be-
tween them. These variants differ in logical expressiveness and in the underly-
ing language paradigms and allow users to make a trade-off between provided
expressiveness and the implied complexity of ontology modeling on a per-
application basis. The variants are as follows:

(a) Language variants (b) Layering

Fig. 7.1. WSML variants and layering

• WSML-Core is based on the intersection of the description logic SHIQ

and horn Logic, called DLP (description logic programs) [50]. It has the
least expressive power of all the WSML variants. The main features of the
language are concepts, attributes, binary relations, and instances, as well
as concept and relation hierarchies and support for datatypes.

• WSML-DL captures the description logic SHIQ ( D ), which is a major

part of the DL species of OWL [32].

• WSML-Flight is an extension of WSML-Core which provides a powerful

rule language. It adds features such as metamodeling, constraints, and
nonmonotonic negation. WSML-Flight is based on a logic programming
variant of F-Logic [72] and is semantically equivalent to datalog with in-
equality and (locally) stratified negation. WSML-Flight is a direct syntac-
tic extension of WSML-Core, and it is a semantic extension in the sense
that the WSML-Core subset of WSML-Flight agrees with WSML-Core on
ground entailments (see [70]).