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organickm ContextualismThis paper presentsfour world views for developing system spec@cations. Each is described by first revealing its root metaphor, that is, the most primitive starting point for understanding a system As each world view and its metaphor are described, we show how particular major current approaches to systems analysis and design fall within the view. We discuss how the root metaphor simultaneously provides useful system concepts while limiting their utility. The paper concludes by suggesting how practicing analysts can use world views to guard against missing important system aspects, avoid specification complexity, and ensure greater coverage and completeness.logical database Behavior, measurable goals ("intentions") and perfomme of the system Humadsystem interface ("conversations"), utility and

TM SADT, Structured Analysis and Design Technique, is a graphical language for describing systems.In this paper we indicate the role of SADT in software design.The graphical language provides a powerful design vocabulary in which a designer can conciselyand unambiguously express his design.SADT is compatible with widely used contemporary design methodologies including Structured Design and the Jackson method.

Landin's SECD Machine does not completely compute certain expressions of the k-calculus and so is modified by the addition of an output component and a unique name counter.This modified machine is proven to correctly implement the k-calculus.