Projectional Language Workbenches as a Foundation for Product Line Engineering

In this paper I explain the benefits of projectional language workbenches for product line engineering. The ability to extend programming languages with domain specific concepts, mix programs (i.e. descriptions written in general purpose languages) and models (i.e. descriptions expressed with DSLs) and also overlay configurative variability to both of these promises highly integrated and productive tools for product line development. 1 Variability in PLE In the context of product line engineering, DSLs are used to bind variability. We distinguish between two kinds of variability: structural and non-structural. Structural variability is described using creative construction DSLs, whereas non-structural variability can be described using configuration tools. Structural variability is unbounded, whereas configuration variability is usually bounded. Figure 1 illustrates the spectrum of languages commonly used for expressing and binding variability, reusing an illustration by Krzysztof Czarnecki [6]. Figure 1 Spectrum of Variability Let's look at two well-known ways of representing variability. Figure 2 shows the meta model of a creative construction DSL. Any number of models can be defined, by instantiating meta model elements. Figure 3 presents an example using the familiar concrete syntax of UML.