Programming languages for relational data base systems

ion The concept of data abstraction has received much attention in the programming language community. Recently, there has been interest in the use of data abstraction with respect to data base systems. 18 Many data base systems support abstraction related facilities such as views, integrity constraints and triggers. 3,12,19,33 For example, a view provides a form of abstraction in that the user can construct queries for relations which do not actually exist but are materialized from a number of relations. If the organization of the relations is changed, the view can be maintained by redefining it in terms of this new organization. In addition, some authors have proposed mechanisms for specifying higher level operations on data bases (such as "hire" and "fire").18 Although some systems offer these abstraction * Requests can be changed at run-time (e.g., in EQUEL relation and domain names can change dynamically). From the collection of the Computer History Museum (www.computerhistory.org) facilities, they have not yet integrated them with their counterparts in data abstraction from programming languages. * AN INTEGRATED APPROACH We will now consider the integration of data base objects and operations into a programming language. We will not attempt to give a complete language proposal here. Instead, we shall illustrate some of the benefits of this approach. Our discussion is divided into four areas: type system, data base operations, compilation, and abstraction.