Alphard: Form and Content by Mary Shaw (auth.), Mary Shaw (eds.)

By Mary Shaw (auth.), Mary Shaw (eds.)

Alphard is a layout for a programming process that helps the abstraction and verification strategies required through glossy program'ming technique. in the course of the language layout method, we have been involved concurrently with difficulties of method, correctness, and potency. Methodological matters are addressed via amenities for outlining new, task·specific abstractions that seize complicated notions by way of their meant houses, with no explicating them by way of particular low· point implementations. suggestions for verifying sure houses of those courses handle the correctness issues. eventually, the language has been designed to allow compilation to effective item code. even if a compiler was once no longer applied, the examine make clear specification matters and on programming technique. an abstraction, specifying its habit Alphard language constructs enable a programmer to isolate publicly whereas localizing wisdom approximately its implementation. The verification of such an abstraction includes exhibiting that its implementation behaves in response to the general public specification. Given this sort of verification, the abstraction can be used with self belief to build higher·level, extra summary, courses. the commonest form of abstraction in Alphard corresponds to what's now referred to as an summary info kind. An summary information sort contains a suite of values for parts of the sort and a suite of operations on these values. a brand new language build, the shape, offers the way to encapsulate the definitions of knowledge constructions and operations in the sort of means that purely public info might be accessed via the remainder of the program.

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T. Baker, "Chief Programmer Team Management of Programming", IBM S,stems JournQL, II, 1, 1972 (pp. 56-73). [Baker72] Frederick P. ,$ on SoftwQre Engineering , Addison-Wesley, 1975. [Brooks75] [BurstaIl74] R. M. Burst all, "Program Proving as Hand Simulation with a little Induction", Proc. of IFIP Congress 74, 1974 (pp. 308-312). [Bu)(ton70] J. N. Buxton and B. ttee. Rome. Itcl,. October 27-31, 1969, NATO, April 1970. Ole-Johan Dahl and C. A. R. -J. Dahl, E. W. R. Hoare), Academic Pres~ 1972 (pp.

Axiomatic techniques (may) avoid these problems at the expense of being less intuitive (at least until one becomes thoroughly familiar with them). We are neither advocating nor rejecting these two techniques here; Alphard should accommodate both, and we have chosen one we are comfortable with. In this paper, we shall presume the existence of a suitable collection of recognized mathematical entities, such as integers, booleans, sets, sequences, multisets, matrices, and the operations defined on these entities.

It should not require that: (1) the vectors be of some prespecified length, (2) the upper and/or lower bounds of these vectors have some prespecified value, or (3) the elements have any other properties. The "<>" notation provides a means of specifying the required properties of actual parameters. tifiers to permit the specification of non-requirements. xyz"j they appear in formal parameter lists and are assigned meaning from the corresponding actual parameters. identifier are required to have the same meaning in the same scope.

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