Information Technology Reference
In-Depth Information
Cardinality on Group Features.
In a constraint
C =
[M, F, A =[i..j],D]
where
F
is a group feature,the meanings of
i
and
j
are respectively the minimum and maximum number of
features grouped by
F
that can be bound to a particular model
element that conforms to
M
.
Forexample,forarequirementoftheproductlinespecifying
that lock doors control can be managed by using either
keypad or fingerprint, the product line architect creates
a constraint using the
Room
metaconcept and the
Lock
Door Control
feature,
constraint2
=
Door
,
Lock Door
Control
,A,D]
(see Figure 5.2). The architect sets the
cardinality
A =[..1]
, constraining to zero or one the
number of grouped features (
Fingerprint, Keypad
) that
can be bound to a
Door
element. Thus a door, e.g. the
livingRoomD1
(Figure 5.1), can be bound to only one of the
features
Keypad
or
Fingerprint
.
When a group feature
F
has the cardinality
[n..m]
, the
cardinality of a constraint
C =[M,F,A, D]
has to be inside the
limits of the cardinality of
F
. It implies that if the cardinality
A =[i..j]
then
n ≤ i ≤ j ≤ m
. This ensures that constraint
models are consistent with feature models used for their
construction.
5.2.4.
The structural dependency property
D
EFINITION
5.4.-
The structural dependency property
D
in a
C =[M,F,A, D]
, denotes conditions that model elements have
to satisfy to be bound to specific features.
An example from requirement
R3
presented before is that
automatic windows must have sensors. In this case, the model
elements we identified in the conditions are
Window
and
Sensor
, and the feature is
Automatic Windows
. Thus, to
bind a
Window
element to the
Automatic Windows
feature,
allowedbythe
constraint1
,the
Window
elementshouldhave
a
Sensor
element.
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