(A) study on the decentralized authorization in a data base system

Abstract

A distributed data base system needs the decentralization of data base administrative functions, especially authorization functions, to avoid bottlenecks and support local autonomy. A decentralized authorization needs some other mechanisms in the view of administrators, in contrast to user``s view in a centralized data base system. Most of previous work for authorization mechanism are concerned with the centralized authorization. A model for the decentralized authorization, allowing onelevel delegation, has been studied. But, it is not suitable for general cases. This thesis proposes a general model for decentralized authorization, which can support multi-level delegation. The key concept of this model is the use of delegation graph containing the history of delegation. Delegation graph is useful to the dynamic delegation and recall. It also presents algorithms for delegation and recall under this model. Some assessment of this mechanism is made by comparing with the previous results.