Andrzej Jodlowski, Kazimierz Subieta

Dynamic Object Roles in the Conceptual Modeling and Databases

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Abstract

The report is an overview of issues related to the conceptual modeling of dynamic object roles and to potential applications of this concept for the construction of object database management systems and query languages. We present motivations and goals of the concept and discuss proposals that we have found in the literature. We propose a new approach to dynamic object roles, which assumes that a role is a semantically specific subobject of a given object. Such a subobject inherits dynamically properties of the object (attribute values and methods). The object can be accessed through its name, as well as through the name of any of its current roles. In this setting the role concept is orthogonal to other notions of object-orientedness, such as classes, inheritance, associations and aggregations. The approach enables us to involve the dynamic role concept in an object query language built in the ODMG OQL style. As a formal basis of such a language we assume the stack-based approach to object query languages. Due to the proposed approach the dynamic role on the one hand can be a useful conceptual modeling facility, and on the other hand, can be a feature of data structures, query languages and programming languages implemented in object database management systems.

Key words: dynamic object role, conceptual modeling, query language, object database, database view, inheritance, multiple inheritance, stack-based approach.