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20.10.  Guard

A guard is associated with a transition. At the time an event is dispatched, the guard is evaluated, and if false, its transition is disabled. In the UML metamodel, Guard is a child of ModelElement.

A guard is shown on the diagram by the text of its expression in square brackets ([]).

20.10.1.  Guard Details Tabs

The details tabs that are active for guards are as follows.

ToDoItem

Standard tab.

Properties

See Section 20.10.2, “ Guard Property Toolbar and Section 20.10.3, “ Property Fields For Guard below.

Documentation

Standard tab.

Stereotype

Standard tab, containing the stereotypes for the guard. In the UML metamodel, Guard has no standard stereotypes defined.

Tagged Values

Standard tab. In the UML metamodel, Guard has no standard tagged values defined.

20.10.2.  Guard Property Toolbar

Go up

Navigate up through the package structure.

New Stereotype

This creates a new Stereotype (see Section 16.6, “ Stereotype) for the selected guard, navigating immediately to the properties tab for that stereotype.

Delete from Model

This deletes the guard from the model

[Warning]Warning

This is a deletion from the model, not just the diagram.

20.10.3.  Property Fields For Guard

Name

Text box. The name of the guard. By convention guard names start with a lower case letter and use bumpy caps to divide words within the name.

[Note]Note

ArgoUML does not enforce this naming convention.

Transition

Text box, showing the transition that owns this guard.

Button 1 double-click on the transition navigates to that transition.

Expression

Text box. The expression that defines the guard.

Language

Text box. This indicates that the expression is written in a particular interpretation language with which to evaluate the text.