In this paper, we first made a
parallel between the syntax of programming languages and the structure
of Web sites (or semi-structured documents), and between the semantics
of programs and the semantics of Web sites, applying some notions of
types and semantic rules to documents on the Web. Then we argued that
Natural Semantics (traditionally used to specify the semantics
of programming languages) was a powerful tool to address the problem
of Web site (static) semantics specification i.e. semantic verifications
which is crucial for supporting the design and the
maintenance of Web sites.
A test implementation of our ideas has been done using the Centaur
system using its semantics specification formalism Typol to
construct a prototype of a Web site verification system by means of
inference rules using natural semantics
[Kahn1987,Despeyroux1988,Borras et al.1988,Jacobs and Rideau-Gallot1992].
This test example has been done for two classes of
XML-based Web sites: thematic directories and institutional sites.
The use of natural semantics shows clearly the difference between syntactical
checking (for example verifying a page against a DTD, like in an XML
validator) that is context-free, and a semantic computation that is
context-dependent. The example of thematic directory shows also the
possibility of using external resources tools (thesauri, ontologies).
The overall experience is positive and needs to be confirmed
with more real applications. However, two main problems must be
addressed in the future: first, the Typol language is heavy to use in such a context
(some rules must be given for each node of the abstract syntax tree
i.e. each tag, and every action on the environment must be specified
in great details), it seems necessary to be able to get default or
generic rules, to define a more intuitive syntax and to offer
a way for capitalising experiments; second, as we need to perform
global computation on Web sites we need to get a less monolithic
implementation of the system.
Acknowledgments We want to thank Hacene Cherfi (student from
Paris-XVII University), for its participation
at the first steps of this work.