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The possibility to define constraint models. Using the constraint templates it is
possible to specify specific constraints for a particular process.
The verification capabilities of DECLARE. While modeling or redesigning work-
flows errors may be introduced. Hence, DECLARE offers a wide range of verifi-
cation capabilities.
The enactment of constraint model instances. Based on such constraint lan-
guages, DECLARE can automatically generate the support needed, that is, manda-
tory constraints can not be violated while optional constraints are used to
generate warnings.
The possibility to change constraint models and to migrate instances. Although
DECLARE allows for a declarative way of modeling, other flexibility issues such
as migrating cases are supported.
The integration of YAWL and DECLARE. As explained using Fig. 12.1, it is
rather easy to support an arbitrary nesting of workflow languages.

12.3 Constraint Templates

An arbitrary number of constraint-based languages can be defined in DECLARE.
For example, Fig. 12.4 shows how the ConDec language (cf. Chap. 6) is defined in
the Designer tool. A tree with the language templates is shown under the selected
language. the selected template is presented graphically on the panel on the right
side of the screen.
An arbitrary number of templates can be created for each language. Figure 12.4
shows a screenshot of the Designer while defining the precedence template. First,
the template name and additional label are entered. Next, it is possible to define an
arbitrary number of parameters in the template. The precedence template has two
parameters: A and B. For each parameter it is specified whether it can be branched or
not. When creating a constraint from a template in a model, a task replaces each of
the template’s parameters. If a parameter is branchable, then it is possible to replace
the parameter with more tasks. In this case, the parameter will be replaced by a
disjunction of selected tasks in the formula (cf. Chap. 6). The graphical representa-
tion of the template is defined by selecting the kind of symbol that will be drawn
next to each parameter and the style of the line. Figure 12.4 shows that the response
template is graphically represented by a single line with a filled arrow-and-circle
symbol next to the second task (B). Furthermore, a textual description and the LTL
formula are given.

12.4 Constraint Workflow Models

Constraint models can be developed in the Designer tool after selecting one of the
languages defined in the system. In this chapter, we use only the ConDec tem-
plates described in Chap. 6. However, as explained before, DECLARE is extensible
and multilingual. As an example, we consider the Less than Truck Load (LTTL)