Towards a New Model of Abstraction in Software Engineering

ion In Action I want to start by talking about the current view of abstraction in software engineering: how we use it, what the principles are, what the terminology is and what it does for us. Rather than attempting any sort of formal definition, I will just use an example. I will talk about the implementation of a familiar system, using familiar terms of abstraction, with the goal of getting the terminology I am going to use out on the table. Consider the display portion of a spreadsheet application. In practice, the implementation would be based on “layers of abstraction” as shown in Figure 1. The spreadsheetwould be implemented on top of a window system, which would in turn be implemented on top of an operating system and so on down (not very far) to the machine. The horizontal lines in the figure are commonly called “abstraction barriers,” “abstractions” or “interfaces.” Each provides useful 3333 Coyote Hill Rd., Palo Alto, CA 94304; (415)812-4888; [email protected]. c 1992 Xerox Corporation. All Rights Reserved. Spreadsheet Application