Software Product Line Engineering Basics - Model-Driven and Software Product Line Engineering - page 40

used to define a specific domain in terms of their mandatory ,
optional ,or alternative characteristics. The commonalities are
represented as a tree of mandatory features. Optional denotes
characteristics specific to some products and alternatives
express a choice between several variants.
Extensions have been introduced to increase the expressive
power, such as feature cardinality, groups and group
cardinality, and attributes for features. The purpose of these
extensions is to restrict the set of variants that can be selected
from feature models to create particular configurations. One
of the most cited works on feature modeling was done
by Czarnecki et al . [CZA 04], where the authors propose
a cardinality-based notation for feature modeling including
solitary , group ,and grouped features.This approach integrates
a number of existing extensions of previous approaches; thus,
we suggest the use of this notation.
Figure 2.5 presents a feature model including alternative
Smart-Homes' facilities. One FeatureGroup appears for each
group of facilities. The Lock Door Control feature groups
the features Fingerprint and Keypad and has cardinality
[0..1] , which implicitly means that Door elements can have
either keypad, fingerprint, or none of them as lock door control
mechanisms. The Environmental Control feature groups
the features Air Conditioning and Automatic Windows
and also has cardinality [0..1] , which implicitly means
that Room elements can have either automatic windows, air
conditioning, or none of them as lock environmental control
mechanism. We say implicitly because there is no semantics in
traditionalfeaturemodelsorinmetamodels,toformallydenote
that features represent variants that affect particular model
elements.
Figure 2.6 presents another example to illustrate the
concepts introduced by Czarnecki et al . by using a feature
model of an operating system security profile [CZA 04].