The Two Facets of Object-Oriented Data Models

request to the contrary. Technical papers are unre formed. Committee is open to individuals who demonstrate willingness to actively participate in the various acti vities of the TC. A member of the IEEE Computer Society may join the TC as a full member. A non— member of the Computer Society may join as a par ticipating member, with approval from at least one officer of the TC. Both full members and participat ing members of the TC are entitled to receive the quarterly bulletin of the TC free of charge, until fur ther notice. This issue presents a sampling of some recent attempts to provide a theoretical foundation for object-oriented database systems. The issue cuntains 12 papers. These papers cover various aspects of object-Abiteboul and Kanellakis point out the two facets of object-oriented data models — structural and behavioral — that reflect the two origins of object-oriented database systems — relational database theory and object-oriented programming. They formalize and analyze these two facets and give examples of their integration. Been argues for the extension of the existing logic-based approaches to databases and programming languages for modeling object-oriented database systems. He presents an initial model approach that unifies the theories of relational databases, deductive programming, and abstract data types. He also argues for functions as first class values and a flexible function definition facility to model behavioral aspects of object-oriented database systems. Kifer presents the salient features of F-logic that make it possible to provide a full logical formalization of object-oriented languages. F-logic breaks the distinction between classes, objects, and attributes which allows queries that may return sets of attributes, classes, or any other aggregation that involves these higher-order entities. It is also possible to define parametric classes in F-logic. argue that the object-oriented database systems can be best understood in the framework of typed languages. They address the demands placed on programming languages by the addition of operations on records and " bulk " data types such as sets. Lecluse and Richard describe the foundations of the 02 database system. The 02 data model differentiates between values and objects, and between types and classes. It also supports the notions of the consistency of a class hierarchy and database schema. Zdonik and Mitchell present the ENCORE data model and its query algebra, called EQUAL. This algebra generalizes relational operations by providing the capability to access and produce encapsulated, logically complex objects. …