A Specification Language for Digital Systems

Abstract

The work reported in this thesis is concerned with the selection of a formal language for practical use in industry for writing specifications of systems containing both hardware and software. The aims of using such a language are to improve the communication of requirements and to increase the number of errors detected at an early stage of the design process. Due to the size of the audience of writers and readers of these specifications, one additional aim is to minimise the amount of training which will be required by these people. Apart from its formality, the language must therefore be able to describe large and complex systems in a comprehensible manner. Criteria for the evaluation of candidate languages are derived from these needs and then used in a review of a large number of languages from published sources. All those reviewed were found to be deficient in some respect, so a new language was designed to fulfill the criteria. This language was named ASL, being an acronym for "A Specification Language"; it is suitable for use in specifying all information-processing systems where the received and transmitted information can be treated as discrete (i.e. digital) signals. In order to confirm the suitability of ASL, a number of practical trials of the language were carried out. Although these were of limited size, they did cover both hardware and software systems and personnel. The results of these trials, including suggestions from the participants for improvements to ASL, are discussed as part of the evaluation of the success of the project.