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184 M. Pesic
ConDec language. ConDec provides more than 20 constraint templates, among
which are the ones depicted in Fig. 6.5. ConDec templates are structured into three
groups: (1) Existence templates specify how many times or when a task can be
executed, for example, init and existence templates; (2) relation templates define
some relation between two (or more) tasks, for example, response, precedence,
and succession;(3) negation templates define a negative relation between tasks, for
example, not coexistence; and (4) choice templates define a choice between tasks,
for example, 1of 4.
Figure 6.7 depicts the relation between constraint templates, constraints, and
models for ConDec. At the template abstraction level, templates are defined on a
predefined number of abstract parameters (e.g., parameter A and B). When a con-
straint is specified, the abstract parameter is replaced by a concrete one, for example,
in Fig. 6.7 the left precedence constraint concretizes abstract parameter A from the
precedence template with concrete parameter bill. A “plain” constraint is a con-
cretization of the predefined parameters of a constraint template (cf. Fig. 6.6). Each
constraint can easily be extended to deal with more parameters than defined by its
template by the means of branching.
Every ConDec template involves a specific number of tasks. For example, tem-
plates existence(A), precedence(A,B),and 1 of 4(A,B,C,D) involve one, two, and
four tasks, respectively. When a constraint is created based on a template, the con-
straint will involve as many real tasks as predefined in the template. Templates can
be reused to specify different constraints, as shown for the precedence template in
Fig. 6.7. Finally, constraints from the ConDec constraint templates can be used to
specify ConDec models.

GRAPHICAL LTL FORMULA
TEMPLATE A B (! A) W B

‘PLAIN’
pickup bill (! bill) W pickup
CONSTRAINT
pickup
BRANCHED
CONSTRAINT
bill (! bill) W (pickup \/ deliver)
delivery
A1
BRANCHED
CONSTRAINT A2 (! B) W (A1 \/ A2 \/ … \/ AN)
TO MULTIPLE B
TASKS ...
AN

Fig. 6.6 Branching the response template