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7.5 Key Features of WSML
There are a number of features which make WSML unique in comparison
with other language proposals for the Semantic Web and Semantic Web ser-
vices. These key features are mainly due to the two pillars of WSML: (1)
a
language-independent conceptual model
for ontologies, Web services, goals,
and mediators, based on WSMO [116] and (2) the
reuse
of several well-known
logical-language paradigms in
one
syntactical framework. More specifically,
we see the following as the key features of WSML:
•
One syntactic framework for a set of layered languages.
We believe differ-
ent Semantic Web and Semantic Web service applications need languages
of different expressiveness and that no single language paradigm will be
su
cient for all cases. With WSML, we are investigating the use of de-
scription logics and logic programming for Semantic Web services.
•
Normative, human-readable syntax.
It has been argued that tools will hide
the syntax of the language from the user; however, as has been seen, for
example with the adoption of SQL, an expressive but understandable syn-
tax is crucial for successful adoption of a language. Developers and early
adopters of the language will have to deal with the concrete syntax. If it
is easy to read and understand then it will allow easier adoption of the
language.
•
Separation of conceptual and logical modeling.
On the one hand, the con-
ceptual syntax of WSML has been designed in such a way that it is in-
dependent of the underlying logical language, such that no or only lim-
ited knowledge of logical languages is required for the basic modeling of
ontologies, Web services, goals, and mediators. On the other hand, the
logical-expression syntax allows expert users to refine the definitions of
the conceptual syntax using the full expressive power of the underlying
logic.
•
Semantics based on well-known formalisms.
WSML captures well-known
logical formalisms such as datalog and description logics in a unifying
syntactical framework while maintaining the established computational
properties of the original formalisms through proper syntactic layering.
The variants of WSML allow the reuse of tools already developed for
these formalisms. Notably, WSML allows the reuse of e
cient querying
engines developed for datalog and e
cient subsumption reasoners devel-
oped in the area of description logics. Interoperation between paradigms
is achieved through a common subset, WSML-Core, based on description
logic programs [50].
•
WWW language.
WSML has a number of features which integrate it seam-
lessly with the Web. WSML adopts the IRI standard, the successor of
the URI, for the identification of resources, following the Web architec-
ture. Furthermore, WSML adopts the namespace mechanism of XML,
datatypes in WSML are compatible with datatypes in XML Schema [16],
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