Access Control and Semantic Web ◾ 39
ontologies have to be secure. at is, access to the ontologies has to be controlled.
is means that different users may have access to different parts of the ontology.
On the other hand, ontologies may be used to specify security policies just as XML
and RDF have been used to specify the policies. at is, we will describe how
ontologies may be secured as well as how ontologies may be used to specify the
various policies.
Secure query and rules processing: e layer above the secure RDF layer is the
secure query and rule processing layer. While RDF can be used to specify security
policies (see for example Carminati et al. 2004), the Web rules language being
developed by W3C is more powerful to specify compl