Extending an Object-Oriented Model: Multiple Class Objects

Experiences of both researchers and practitioners with the development of object-oriented database systems help us to evaluate the real contributions of object-oriented modeling principles and show the limits and possibilities of improvements of the object-oriented model. One of the research areas where such a need was recognized concerns the class membership. In most object-oriented data model objects must belong to a single most specific class. However, the real world situations often break this presumption. The aim of this paper is to discuss the issues relating to an extension of modeling concepts to capture the objects that can belong to the multiple most specific classes. Our final objective is to present a framework for the formal object-oriented models that will provide the rigorous theoretical tool to solve issues concerning conflicts that can arise in structural components of objects. Most importantly, we show that the structural conflicts can be solved from the context determined by the static typing.