Formalizing Reusable Software Components

There has been a long-standing desire in computer science for a way of collecting and using libraries of standard software components. Unfortunately, there has been only limited success in actually doing this. We believe that the lack of success stems not from any resistance to the idea, nor from any lack of trying, but rather from the difficulty of choosing an appropriate formalism for representing components. In this paper we define five desiderata for a good formalization of reusable software components and discuss many of the formalisms which have been used for representing components in light of these desiderata. We then briefly describe a formalism we are developing the Plan Calculus which seeks to satisfy these desiderata by combining together the best features of prior formalisms. This paper has been accepted by the ITT Workshop on Reusability in Programming, Newport RI, September 7-9, 1983. A.I. Laboratory Working Papers are produced for internal circulation, and may contain information that is, for example, too preliminary or too detailed for formal publication. It is not intended that they should be papers to which reference may be made in the literature. QMassachusetts Institute of Technology, 1983