PROGRES for Beginners

This paper is an informal introduction to currently distributed version of PROGRES. We will use a single running example, the specification of a small software design and configuration tool, to present its most important constructs and properties. Although being a kind of "toy" example compared with real software engineering tools, it is complex enough to discuss all important features of the language PROGRES. A complete formal description of PROGRES and its underlying graph rewriting formalism is outside the scope of this paper and may be found in [36, 37]. The paper is organized as follows: section 2 gives a rather short overview of other tool specification languages, discusses their deficiencies and motivates thereby why it was necessary to develop a specification language like PROGRES. Section 3 explains our running example. Section 4 shows how software engineering documents are internally represented by attributed graphs and how graph schema definitions may be used to characterize the static properties of a class of internal documents. Section 5 and section 5 deal with the definition of rather complex document querying and manipulating processes as subgraph searching and rewriting programs, whereas section 7 discusses advanced features for improving the runtime behavior of specifications and for writing highly reusable specifications. Section 8 summarizes finally the main characteristics of our specification language