Persistent languages facilitate the implementation of software version management

The use of persistent programming languages to construct tools for maintaining the complex modular structure of large-scale application programs transforms the problem into a database maintenance problem. The application construction environment can be considered to be a database of software libraries, and standard database techniques can be used to handle the modules. The persistent language PS-Algol provides a good basis for manipulating such libraries, as it has the appropriate graphics facilities, first-class procedures, delayed binding, delayed type-checking, strong type-checking and a compiler callable at run-time. It is shown how these features help by concentrating on two issues: module version management and the control over the binding together of two modules. Some simple facilities for managing a software database are outlined, and implementation techniques equally applicable to more sophisticated systems are described