It is the thesis of this work than many computer software systems being built today are similar and should be built out of reusable software components.

The appropriate use of software components is investigated by analogy to the classical engineering question of whether to build an object out of custom-made parts or standard parts and assemblies. The same analogy is used to explain some of the problems with previous work on reusable software. The result of reasoning with the engineering analogy is that the reuse of software results only from the reuse of analysis, design, and code; rather than just the reuse of code.