Object-oriented databases

In this thesis, we investigate the different proposed ways of combining object oriented and relational database systems (such combined systems are commonly called object-relational systems). This thesis is based on ideas presented in various papers about object and object relational databases. In this work, a discussion of standards such as ANSI's SQL3 (to be released) and ODMG-93 is given. In particular, the "Class = Relation" and "Class = Domain" approaches to object-relational systems are investigated. Arguments supporting the proposition that the latter approach is the correct approach are presented.

The use of formal methods has become increasingly important for software development. In this thesis, we present the formal specifications for a method-based authorization model for object-oriented databases. We also formalize a proposed user group structuring. We start from an existing OMT (Object Modeling Technique) description and we use Z as language for formal specification. This specification gives a precise definition of the policies and functions of this authorization system. This can be used as a basis for implementation and possible verification in those cases where a high level of security is required.

The incorporation of object-oriented and semantic modeling concepts to databases is one of the most significant advances in the evolution of database systems. Among the many issues brought along by this integration, one that becomes important is the protection of the information. This thesis presents an authorization model that applies two basic aspects: control of users' access to data values, and control of administrators' access to data definitions and authorization rules. The model consists of a set of policies, a structure for authorization rules, algorithms for access request validation and procedures for administrative functions. Even though this model is developed in the context of a particular data model, the discussion is sufficiently general and can be applied to similar environments.