Controlling Access to a Digital Library Ontology - A Graph Transformation Approach

This paper presents a graph-based formalism for an Ontology Based Access Control (OBAC) system applied to Digital Library (DL) ontology. It uses graph transformations, a graphical specification technique based on a generalization of classical string grammars to nonlinear structures. The proposed formalism provides an executable specification that exploits existing tools of graph grammar to verify the properties of a graph-based access control mechanism applicable to a digital library ontology description. It also provides a uniform specification for con trolling access not only at the concept level but also at the level of the documents covered by the concepts including node obfuscation, if required. Authors have shown the need of using both positive and negative authorizations for effective access control to the DL ontology. However, it gives rise to a decidability problem. A view creation mechanism and associated algorithm has been presented as a solution to the decidability problem.