We define a notion of program which is not a computer program but an operator program: a detailed description of actions performed and decisions taken by a human operator (computer user) performing a task to achieve a goal in a simple setting consisting of that user, one or more computers and a work environment. Our definition and notations are based on the program algebra PGA: a small body of theory allowing one to reason fundamentally and practically about programs viewed as instruction sequences. This article is entirely self-contained and introduces all concepts and notations used. We offer some small examples, and we sketch one limitation of our approach. q 2003 Elsevier B.V. All rights reserved.
['Jan A. Bergstra', 'Pum Walters']
Operator programs and operator processes