Integrity constraints and structural modelling in object-orientated databases: A unified approach

Database technology is constantly evolving, with the aim of supporting larger and more complex applications. To this end, more powerful database models have been recently introduced. Along this line, Object-Oriented Databases (ODBs), characterized by rich data and behaviour modelling facilities, appear to be the successors to relational databases. In this paper, we propose to extend the data modelling component of ODBs, to declaratively represent semantic integrity constraints in the database schema. This proposal aims to reduce the portion of code, in methods devoted to verifying the semantic integrity of the data managed by an application. According to the proposed approach, the constraints are specified in the schema rather than in the methods, and the data integrity is enforced automatically by the system. In this paper, a data definition language called TQL+ is proposed, which allows data and integrity constraints to be modelled in a uniform framework. This paper presents both theoretical and experimental aspects. First, TQL+ is based on formal semantics, defined using a denotational approach. Second, TQL+ is the basis of the prototype Mosaico, a software environment aimed at supporting the design and rapid prototyping of ODB applications, developed at IASI.