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View Operations on Objects with Roles for a Statically Typed Database Language

Summary: View Operations on Objects with Roles
for a Statically Typed Database Language
Antonio Albano, Giuseppe Antognoni, and Giorgio Ghelli
To deal with the evolution of data and applications, and with the existence of multiple views for
the same data, the object data model needs to be extended with two di erent sets of operations:
object extension operations, to allow an object to dynamically change its type, and object viewing
operations, to allow an object to be seen as if it had a di erent structure. Object extension and object
viewing operations are related, in that they are both identity-preserving operations; but di erent, in
that object extension may modify the behavior of the original object while object viewing creates
a new view for the original object without modifying its behavior. In this paper a set of object
viewing operations is de ned in the context of a statically and strongly typed database programming
language, which supports objects with roles, and the relationships with object extension and role
mechanisms is discussed. We then show how the object viewing operations can be used to give the
semantics of a higher level mechanism to de ne views for object databases. Examples of the use of
these operations are given with reference to the prototype implementation of the language Galileo 97.
Index Terms|Object databases, object data models, objects with roles, object views, database
programming languages
1 Introduction
The success of the object data model is mainly due to its expressivity and its ability to deal with both


Source: Albano, Antonio - Dipartimento di Informatica, UniversitÓ di Pisa


Collections: Computer Technologies and Information Sciences