An actor represents any external entity (human or machine) that interacts with the system, providing input, receiving output, or both.
Within the UML metamodel, actor is a sub-class of
classifier
.
The actor icon is a stick man (see Figure 16.1, “Possible artifacts on a use case diagram.”).
The details tabs that are active for actors are as follows.
ToDoItem
Standard tab.
Properties
See Section 16.2.2, “Actor Property Toolbar” and Section 16.2.3, “Property Fields For Actor” below.
Documentation
Standard tab. See Section 12.5, “Documentation Tab”.
Style
Standard tab. Fill color is used for the stick man's head.
Source
Standard tab. It would not be usual to provide any code for an actor, since it is external to the system.
![]() | Note |
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The source tab content can be changed, but this has no effect. |
Constraints
Standard tab. ArgoUML only supports constraints on Classes and Features (Attributes, Operations, Receptions, and Methods), so this tab is grayed out.
Tagged Values
Standard tab. In the UML metamodel,
Actor
has the following standard tagged
values defined.
persistence
(from the
superclass, Classifier
). Values
transitory
, indicating state is
destroyed when an instance is destroyed or
persistent
, marking state is
preserved when an instance is destroyed.
![]() | Tip |
---|---|
Actors sit outside the system, and so their internal behavior is of little concern, and this tagged value is best ignored. |
semantics
(from the
superclass, Classifier
). The value is a
specification of the semantics of the
actor.
derived
(from the
superclass, ModelElement
). Values
true
, meaning the actor is
redundant—it can be formally derived from other
elements, or false
meaning it
cannot.
![]() | Note |
---|---|
Derived actors have limited value, since they sit outside the system being designed. They may have their value in analysis to introduce useful names or concepts. |
Go
up
Navigate up through the package structure of the model.
Add Actor
This creates a new actor within the model, (but not within the diagram), navigating immediately to the properties tab for that actor.
![]() | Tip |
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This method of creating new actors can be confusing. Much better to create them within diagrams where you want them. |
Delete
This deletes the selected actor from the model.
![]() | Warning |
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This is a deletion from the model
not just the diagram. To delete an actor
from the diagram, but keep it within the model, use the main
menu |
Name
Text box.
The name of the actor.
Since an actor is a
classifier, it would be conventional to Capitalize the first
letter (and initial letters of any component words),
e.g. RemoteSensor
.
![]() | Note |
---|---|
ArgoUML does not enforce any naming convention for actors |
Stereotype
Drop down selector.
Actor is provided by default with
the UML standard stereotypes (metaclass
,
powertype
, process
,
thread
, utility
) for
classifiers.
Stereotypes are of limited value with actors.
The stereotypes
machine
,
organization
,
person
and
singleton
are probably of most use.
However, they are not provided by default with ArgoUML.
Navigate Stereotype
icon. If a
stereotype has been selected, this will navigate to the
stereotype property panel (see Section 15.4, “Stereotype”).
Namespace
Text box. Records the namespace for the actor. This is the package hierarchy.
Modifiers
Check box, with entries
Abstract
,
Leaf
and
Root
.
Abstract
is used to declare
that this actor cannot be instantiated, but must always be
specialized.
![]() | Caution |
---|---|
While actors can be specialized and generalized, it is not clear that an abstract actor has any meaning. Perhaps it might be used to indicate an actor that does not itself interact with a use case, but whose children do. |
leaf
indicates that this
actor can have no further children, while
Root
indicates it is a top level
actor with no parent.
Generalizations
Text area. Lists any actor that generalizes this actor.
Button 1 Double Click navigates to the generalization and opens its property tab.
Specializations
Text box. Lists any specialized actor (i.e. for which this actor is a generalization. The specialized actors can communicate with the same use case instances as this actor.
button 1 click navigates to the generalization and opens its property tab.
Association Ends
Text area. Lists any association ends of associations connected to this actor.
Button 1 Double Click navigates to the selected entry.