This is a common situation since companies have hardly ever
made all the product features to be selected.
Figure 10.3 illustrates the spectrum of variability. Wizards and feature-based
con?¬?guration focus on making choices among known decisions and features.
Domain-speci?¬?c languages do not set choices explicitly but give a practically in?¬?nite
space to set variation.You do not knowall variants, as they can be numerous. There are
as many variants as there are ways to instantiate the metamodel.
In the simplest case of modeling language design, the variability can be
represented solely as properties of modeling objects??”something similar to parameter
FIGURE 10.3 Spectrum of variability (modi?¬?ed from Czarnecki, 2004)
IDENTIFYING AND DEFINING MODELING CONCEPTS 235
lists. The possible values a given property may have can be de?¬?ned as a list containing
the prede?¬?ned legal values of that variability point. In a little more complex cases, and
similar to feature models, variability can be expressed via connections between
modeling elements, their linkages to submodels, and so on. Language concepts may
also be rich enough to allow creating totally new implementations in the variation
space set by the language. In this way, all the variants do not need to be made yet, or
even thought about, since the creation of new variants can be done by creating totally
new speci?¬?cations.
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