Defining database views as data abstractions in EXT_ Pascal

摘要

Data abstraction mechanisms suitable for defining relational database views in high level programming languages are described. The abstraction mechanisms are incorporated into Pascal resulting in EXT_Pascal. The data abstraction mechanisms are the module and the abstract type construct. A database application program's database view is encapsulated within a single module. A database view consists of a nonempty collection of relations and a set of operations for updating the relations. The tuple, baserelation, viewrelation and generator types are introduced to facilitate the definition and manipulation of database views.