Resolving authorization conflicts by ontology views for controlled access to a digital library

Purpose – This paper provides a new Digital Library architecture that supports polyhierarchic ontology structure where a child concept representing an interdisciplinary subject area can have multiple parent concepts. The paper further proposes an access control mechanism for controlled access to different concepts by different users depending on the authorizations available to each such user. The proposed model thus provides a better knowledge representation and faster searching possibility of documents for modern Digital Libraries with controlled access to the system. Design/methodology/approach – Since the proposed Digital Library Architecture considers polyhierarchy, the underlying hierarchical structure becomes a Directed Acyclic Graph instead of a tree. A new access control model has been developed for such a polyhierarchic ontology structure. It has been shown that such model may give rise to undecidability problem. A client specific view generation mechanism has been developed to solve the problem. Findings – The paper has three major contributions. First, it provides better knowledge representation for present-day digital libraries, as new interdisciplinary subject areas are getting introduced. Concepts representing interdisciplinary subject areas will have multiple parents, and consequently, the library ontology introduces a new set of nodes representing document classes. This concept also provides faster search mechanism. Secondly, a new access control model has been introduced for the ontology structure where a user gets authorizations to access a concept node only if its credential supports it. Lastly, a client-based view generation algorithm has been developed so that a client’s access remains limited to its view and avoids any possibility of undecidability in authorization specification. Research limitations/implications – The proposed model, in its present form, supports only read and browse facilities. It would later be extended for addition and update of documents. Moreover, the paper explains the model in a single user environment. It will be augmented later to consider simultaneous access from multiple users. Practical implications – The paper emphasizes the need for changing the present digital library ontology to a polyhierarchic structure to provide proper representation of knowledge related to the concepts covering interdisciplinary subject areas. Possible implementation strategies have also been mentioned. This design method can also be extended for other semantic web applications. Originality/value – This paper offers a new knowledge management strategy to cover the gradual proliferation of interdisciplinary subject areas along with a suitable access control model for a digital library ontology. This methodology can also be extended for other semantic web applications.