Business Modeling and Software Design by Boris Shishkov

Author:Boris Shishkov
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

([OCL]) TimeEvent (/ Effect)

[OCL] (/ Effect)

The first transition type will take place when ExternalEvent takes place and the OCL condition is true. If there is a tag, then the result of the execution of ExternalEvent must coincide with tag for the transition to take place. The second transition will take place when there is a TimeEvent and the OCL condition is true. If there is an Effect, the changes specified by it will also be made. Finally, the last transition type is similar to the second excepting the occurrence of a time event. These transition types cover the types of transitions allowed in the UML 2.4.1 specification that are significant at the specification level, as explained in [30].

An ExternalEvent will have as input parameters the artifacts in whose transitions it appears or the identifiers of those artifacts. The execution of these events and their respective tags (if any) will be defined in an activity diagram. Effects correspond to atomic tasks that have as input parameters the artifacts involved in the transition.

OCL is an OCL expression which starts from self or Class.allInstances()->... where Class is any of the classes in the class diagram. A TimeEvent represents an occurrence of time. We distinguish between relative and absolute time expressions. An absolute expression has the form at(time_expression); a relative expression has the form after(time_expression).

Notice that this state machine diagram does not follow exactly the UML standard described in [22]. This is due to the fact that it has tags, which we use to determine whether the event ends successfully or not. In traditional UML state machine diagrams, events are atomic and there is no need for such conditions.

In addition, we also allow more than one outgoing transition from the initial node. This is useful when the artifact can be created in different ways. Alternatively, this situation could be represented using one outgoing transition from the initial node, leading to a state called InitialState. From this state, we could have the outgoing transitions that start from the initial node and leave the rest of the state machine diagram as it is. However, representing the lifecycles in this way does not contribute any relevant information and adds complexity to the final diagram.

Although we use a variant of UML state machines, any other notation based on state machines would be useful to represent the lifecycles of the artifacts.

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