Data abstraction, views and updates in RIGEL

Abstract

Language constructs to support the development of data base applications provided in the programming language rigel are described. First, the language type system includes relations, views, and tuples as built-in types. Tuple-values are introduced to provide more flexibility in writing procedures that update relations and views.Second, an expression that produces sequences of values, called a generator, is defined which integrates relational query expressions with other iteration constructs found in general-purpose programming languages. As a result, relational expressions can be used in new contexts (e.g., as parameters to procedures) to provide new capabilities (e.g., programmer-defined aggregate functions).Lastly, a data abstraction facility, unlike those proposed for other data base programming languages, is described. It provides a better notation to specify the interface between a program and a data base and to support the disciplined use of views.All of these constructs are integrated into a sophisticated programming environment to enhance the development of well-structured programs.