Chapter 16

* Schemas

Symbolic transcriptions of expressions and formulas were used throughout this book for the purpose of referring to specific elements in LePUS3 Codecharts. For example, a method which is visually represented by a superimposition of an ellipse sig over a rectangle cls was symbolically represented as the expression sigcls. Thus, perhaps without noticing, Part I of this book has in effect introduced not one but two specification languages: the visual tokens, which constitute LePUS3, and the set of their symbolic transcriptions, to which we refer as Class-Z. The two design description languages are equally useful, each with somewhat different purposes and appealing to a different audience: where LePUS3 Codecharts capitalize on the benefits of visual languages, Class-Z schemas are designed to resemble predicate formulas in their traditional form. This chapter formally introduces this language and the notion of a schema.

In LePUS3, a specification is articulated as a Codechart. In Class-Z, a specification is introduced using the schema notation. For example, the two terms and the one formula in Codechart 82 (p. 129) translate to the following schema:


More generally, specifications encoded in the schema notation consist of two compartments. The first introduces the terms in the specification, each declared with its respective type and dimension, and the second lists ...

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