Forward and backward analysis of object-oriented database programming languages: an application to static integrity management

In this paper, we propose an efficient technique to statically manage integrity constraints in objectoriented database programming languages. We place ourselves in the context of a simplified database programming language, close to O2, in which we assume that updates are undertaken by means of methods. An important issue when dealing with constraints is that of efficiency. A naı̈ve management of such constraints can cause a severe floundering of the overall system. Our basic assumption is that the runtime checking of constraints is too costly to be undertaken systematically. Therefore, methods that are always safe with respect to integrity constraints should be proven so at compile time. The run-time checks should only concern the remaining methods. To that purpose, we propose a new approach, based on the use of predicate transformers combined with automatic theorem proving techniques, to prove the invariance of integrity constraints under complex methods. We then describe the current implementation of our prototype, and report some experiments that have been performed with it on non trivial examples. The counterpart of the problem of program verification is that of program correction. Static analysis techniques can also be applied to solve that problem. We present a systematic approach to undertake the automatic correction of potentially unsafe methods. However, the advantages of the latter technique are not as clear as those of program verification. We will therefore discuss some arguments for and against the use of method correction. Though our work is developed in the context of object-oriented database programming languages, it can easily be applied to the problem of static verification and correction of object-oriented languages providing pre and post-conditions such as Eiffel.