Quality Assurance in the Presence of Variability - Intentional Perspectives on Information Systems Engineering - page 315

strategy based on model checking technology in Sects. 4 and 5. A conclusion is
provided in Sect. 6.

2 Quality Assurance in the Presence of Variability

This section provides a brief introduction to variability modeling which is a prereq-
uisite for understanding the challenges and solutions for quality assurance in product
line engineering.

2.1 Introduction to Variability Modeling

The central concepts for defining and documenting the variability of a software
product line are variation point and variant. A variation point describes what varies
between the products of a software product line. A variant describes a concrete
instance of a variation point. In case of an online shop product line, for example,
the products can vary in terms of the supported interfaces. A product of the product
line (i.e. a concrete online shop) could then offer an interface for traditional web
browsers while another product offers an interface for mobile phone web browsers.
For the documentation of variability in this chapter, we use the Orthogonal
Variability Model (OVM) that has been developed in our group and which offers
benefits over other variability modeling techniques. In the following, we give a
brief introduction into the OVM together with a small example shown in Fig. 1.
For a more detailed introduction into the OVM, we refer to [19] .

VP VP VP

<<Name>> <<Name>> <<Name>>

[min…max]

V
<<Name>>

V
<<Name>>

V
<<Name>>

V
<<Name>>

V
<<Name>>

Alternative
Choice

Mandatory Optional

Fig. 1 Graphical notation of the orthogonal variability model

In the OVM, variation points are modeled as triangles and variants as rectan-
gles. We furthermore distinguish three types variability dependencies to document
in which way variants of a product line must or can be selected:

• A mandatory variability dependency between a variation point and a variant

describes that this variant must always be selected when the variation point is
considered for the product at hand. A mandatory variability dependency is drawn
as a continuous line.