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5. Related Work
This section reviews existing design frameworks for ontology based semantic Web applications.
Hera [63] is a modeling language for enriching the contents of Web Information Systems with
knowledge resulting from different sources. Its design approach encloses the steps for modeling
the domain knowledge and the hypermedia structure and features, producing respectively the
Conceptual (CM), and the Application (AM) and Presentation Model. The representation syntax
of the application domain is RDF(S). The mapping between each data source schema and the
CM is also defined in RDF. The AM models the contents and navigational links of the
application interfaces in terms of classes and properties in the CM. The Hera approach defines
RQL data extraction mechanisms upon the structure of knowledge contained in the CM. It does
not provide any means for extracting the knowledge structure or for making inferences on it to
derive new relations.
Hera-S [64] covers some of the limitations of Hera, by enabling knowledge update through
hypertext interfaces. The domain is modeled with OWL, and the query language interpreted by
Sesame is SeRQL. Queries are not generated automatically by the system. The developer
expresses the appropriate SeRQL queries and parameters within the body of extraction
components.
These two approaches suffer of some common limitations:
• no automatic means are provided for manipulating the knowledge structure;
• the developer must be aware knowledgeable of OWL, RDF(S), and SeRQL, because no
abstraction on the implementation details of the queries is provided;
• the built architecture is rather monolithic and not open to extensibility.
The Semantic Hypermedia Design Method (SHDM) [65] is an extension of the OOHDM
approach for modeling semantic Web applications. It incorporates the conceptual modeling of
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