a layered approach to software design (ira p. goldstein and daniel g. bobrow)

Abstract: Software engineers create alternative designs for their programs, develop these designs to various degrees, compare their properties, then choose among them. Yet most software environments do not allow alternative definitions of procedures to exist simultaneously. It is our hypothesis that an explicit representation for alternative designs can substantially improve a programmer's ability to develop software. To support this hypothesis, we have implemented an experimental Personal information Environment (PIE) that has been employed to create alternative software designs, examine their properties, then choose one as the production version. PIE is based on the use of layered networks. Software systems are described in networks; alternatives are separated by being described in different layers. We also demonstrate that this approach has additional benefits as a data structure for supporting cooperative design among team members and as a basis for integrating the development of code with its associated documentation.(Xerox PARC Publication #CSL-80-5)