Improving object-oriented software design

To take a slightly simplified view, an object in a program is a variable that can be manipulated only by a prescribed set of procedures. Programs written in almost all programming languages can be designed around the notion of objects. Software engineers are interested in two questions about objects: which objects should be used in the construction of a given program; and what general principles can guide the search for objects? The paper looks at the second of these equations, concentrating on object-oriented designs targeted to programming languages such as Ada (ANSI 1983) and modular-2 (Wirth 1985). Typically, object-oriented design begins by identifying a set of objects, perhaps by looking for nouns within the problem statement, and proceeds by identifying procedures for manipulating those objects, perhaps by looking for verbs in the problem statement. An adequate design is one that contains all the data structures and algorithms needed to solve the problem, parcelled up into procedures and modules of comprehensible size