| Sequential Data Algebra Primitives (1996) | |||||||||||||||
Abstract | |||||||||||||||
| this paper is to develop a family of data type specifications and a particular method for writing such specifications based on the four valued logic of [BBR95]. The method is an informal one cast in a number of design rules for specifications of data algebras. The phrase data algebra is used rather than abstract data type in order to emphasise that the data types are first order many sorted algebras that comply a number of requirements (design rules). The four valued (McCarthyan) logic, the new notations for list operators, the omnipresent divergent and meaningless objects, and the very hierarchy of modules below can be viewed as primitives for data algebra. Because all operations including the logical connectives are sequential in the sense that they inspect their arguments in some definite order this style of data algebra is called sequential data algebra. Evidently what we propose is only a choice from an infinite number of different options. So what is being developed below is in fact a set of primitives for a style of sequential data algebra. Some style of data algebra is needed in order to avoid endless duplication and reinvention in the practice of algebraic specification. The mere presence of module libraries will not suffice to reduce the frequency of these improductive events. More importantly far more standardisation will be needed to obtain a body of algebraic specifications with high credibility. Again libraries as such will not generate confidence. In order to achieve standardisation explicit specification styles are needed. The style of sequential data algebra that we use is characterized by a number of rather restrictive design rules, that simultaneously constitute its rationale. The structuring mechanisms as well as the approach to syntax definition and... | |||||||||||||||
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