Computational Structures

Abstract

In chapter 2 it became apparent that newly introduced object sets never occur “isolated” but always together with operations characteristic of them. Thus the canonical operations termed constructors and selectors belong to composite objects (comp. 2.5 and 2.6); the comparison operator is invariably available for all object sets (comp. 2.4). In chapter 1 we have pragmatically presupposed certain object sets such as bool, nat, int, sequ χ etc. and their characteristic operations.

“If at a given level of refinement one is interested only in the behavioural characteristics of certain data objects, then any attempt to abstract data must be based upon those characteristics, and only those characteristics. The introduction of attributes, e. g. a representation, can only serve to cloud the relevant issues!”

Guttag 1975