When modeling xUML services with the Designer, you may come to a point where the features of BPMN and xUML are not sufficient for your purposes. For this cases, the Designer comes with an Action Script Language that implements the action semantics for UML that have been defined by the OMG™. You can implement operations as action script as described on Using Action Script. Also, expressions of the Action Language are not only used in actions but also for decisions (on the outgoing process flow) to evaluate boolean expressions.
The action script language supports the following language elements:
create statements
set and append statements (optionally with a guard)
object navigation
arithmetic and boolean expressions
operation calls
second order operations such as apply, reduce and select for arrays