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4.4. Using Use Cases in ArgoUML
ArgoUML allows you to draw use case diagrams. When you
create a new project it has a use case diagram created by
use case diagram 1. Select
this by button 1 click on the diagram name in the explorer (the
upper left quadrant of the user screen).
New use case diagrams can be created as needed through
Create Diagram on the main menu bar or on
the Create Diagram Toolbar. They are edited in the editing pane
(the upper right quadrant of the user screen).
To add an actor to the diagram use button 1 click on
the actor icon on the editing pane toolbar (
and then button 1 click at the location where you wish to
place it. The actor can be moved subsequently by button 1
motion (i.e. button 1 down over the actor to select it, move
to the new position and button 1 release to drop the actor in
Multiple actors can be added in one go, by using
button 1 double click on the actor icon. Each subsequent
button 1 click will drop an actor on the diagram. A button 1
click on the select icon (
will stop adding actors.
The actors name is set in its property panel. First
select the actor (if not already selected) on the editing
pane using button 1 click. Then click on the
Properties tab in the details pane. The name is
entered in the name field, and will appear on the
As a shortcut, double button 1 click on the name of the
actor in the editing pane (or just typing on the keyboard
when an actor is selected) will allow the name to be edited
directly. This is a convenient way to enter a name for a new
Having created the actor, you will see it appear in the
explorer (the upper left quadrant of the user screen). This
shows all the model elements created within the UML design. A drop
down at the top of the explorer controls the ordering of
model elements in the explorer. The most useful are the
Package-centric (default) and
Diagram-centric. The latter shows model elements grouped
by the diagram on which they appear.
The procedure for adding use cases is the same as that
for adding actors, but using the use case icon on the editing
pane toolbar ().
By default use cases in ArgoUML do not display their
extension points (for use in extend relationships). You can
show the extension point compartment in one of two
Select the use case in the editing pane with
button 1 click, then select the
tab in the details pane and button 1 click on the
Display: Extension Points check
Use button 2 click over the use case in the editing
pane to display a context-sensitive pop-up menu and from
Show/Show Extension Point
The same approaches can be used to hide the extension
220.127.116.11. Adding an Extension Point to a Use Case
There are two ways to add an extension point to a use
Select the use case on the editing pane with
button 1 click. Then click on the
Extension Point icon (
on the toolbar, and a new extension point with default
name and location will be added after any existing
Add Extension Point icon
is grayed out and unusable until a use case is
Select the use case on the editing pane with
button 1 click and then select its property tab in the
details pane. A button 2 click over the
Extension Points: field will bring up a
context-sensitive pop-up menu. Select
Add to add a new extension point.
If any extension points already exist, they will
be shown in this field on the property tab. The new
extension point will be inserted immediately before the
entry over which the pop-up menu was invoked. This
ordering can be changed later by using the
Move Up and
entries on the pop-up menu.
Whichever method is used, the new extension point is
selected, and its property tab can be displayed in the
details pane. The name and location of the extension point
are free text, set in the corresponding fields of the
An existing extension point can be edited from its
property tab. The property tab can be reached in two
If the extension point compartment for the use
case is displayed on the diagram, select the use case
with button 1 click and then select the extension point
with a further button 1 click. The property tab can
then be selected in the details pane.
Otherwise select the use case and its property
tab in the details pane. A button 1 click on the
desired entry in the
Points field will bring up the property tab
for the extension point in the details pane.
The name and location fields of the extension point
may then be edited.
As a shortcut, where the extension point compartment
is displayed, double click on the extension point allows
text to be typed in directly. This is parsed to set name
and location for the extension point.
Extension points may be deleted, or their ordering
changed by using the button 2 pop-up menu over the
Extension Points field in the use case property
Having created an extension point, it will appear in
the explorer (upper left quadrant of the user screen).
Extension points are always shown in a sub-tree beneath
their owning use case.
To join a use case to an actor on the diagram use
button 1 click on the association icon on the editing pane
Hold button 1 down at the use case, move to the actor and
release button 1 (or alternatively start at the actor and
finish at the use case).
This will create a straight line between actor and use
case. You can segment the line by holding down button 1 down
on the line and moving before releasing. A vertex will be
added to the line, which you can move by button 1 motion. A
vertex can be removed by picking it up and sliding to one end
of the line.
Multiple associations can be added in one go, by using
button 1 double click on the association icon. Each
subsequent button 1 down/motion/release sequence will join an
actor to a use case. Use button 1 on the select icon (
to stop adding associations.
It is also possible to add associations using small
“handles” that appear to the left and right of a
use case or actor when it is selected and the mouse is over
it. Dragging the handle from a use case to an actor will
create an association to that actor (and similarly by
dragging a handle from an actor to a use case).
Dragging a handle from a use case into empty space will
create a new actor to go on the other end. Similarly dragging
a handle from an actor into empty space will create a new use
It is possible to give an association a name,
describing the relationship of the actor to the use case,
although this is not usually necessary. This is done through
the property tab of the association. Such a name appears
alongside the association near its center.
18.104.22.168. Setting Navigation
There are two ways of setting the navigation of an
Use button 2 click on the association to bring up
a context-sensitive pop-up menu. The
Navigability sub-menu has options for
bi-directional navigation (the default, with no arrows)
and for navigability Actor->Use Case and
Use button 1 to select the association and select
its property tab in the details pane. This shows a
Association Ends:, with
entries for each end labeled by the actor or use case
name and its multiplicity. Select the end that should
be at the tail of the arrow with button 1 click. This
brings up the property tab for the association end. Use
button 1 click to uncheck the
This may seem counter-intuitive, but in fact
associations by default are navigable in both
directions (when no arrows are shown). This process
is turning off navigation at one
end, rather than turning it on at the other.
You will see it is possible to give an association
end a name in its property tab. This name will appear at
that end of the association, and can be used to indicate
the role being played by an actor or
use case in an association.
For example a time management system for a business
may have use cases for completing time sheets and for
signing off time sheets. An employee actor may be involved
in both, one as an employee, but the other in a role as
22.214.171.124. Setting Multiplicity
There are two ways of setting multiplicity at the end
of an association.
Button 2 click over the end of an association
will cause a context-sensitive pop-up menu to appear
with a sub-menu labeled
Multiplicity. This allows you to select from
1 (the default),
Bring up the property sheet for the association
end as described for setting navigation (see the second
option in Section 126.96.36.199, “Setting Navigation”
). A drop down menu gives a range of multiplicity
options that may be selected.
The second of these two approaches has a wider range
of options, although ArgoUML does not currently allow the
user to set an arbitrary multiplicity.
4.4.4. Hierarchical Use Cases
UML as originally designed allowed use cases to be organized by
grouping them in packages as well as by specifying relations among
In ArgoUML only the relations mechanism is supported.
All Three of the relations that apply to use cases are supported.
These are include, extend
The procedure for adding an include relationship is
the same as that for adding an association, but using the
include icon from the editing pane toolbar (
to join two use cases.
Since include relationships are directional the order
in which the two ends are selected is important. The
including (main) use case should be
selected first (button 1 down) and the
included (subsidiary) use case second
(button 1 release).
It is possible to name include relationships using
the property tab, but this is rarely done, and will not be
displayed on the use case diagram.
The procedure for adding an extend relationship is
the same as that for adding an include relationship, but
using the extend icon from the editing pane toolbar (
to join two use cases.
As with include relationships, the order of selection
matters. In this case, the extending
(subsidiary) use case should be selected first (button 1
down) and the extending (main) use
case second (button 1 release).
This is the reverse of the include relationship,
but reflects the way that designer's tend to think.
The fact that the extend icon's arrow points upward
(the opposite of the include icon) should help remind you
To set a condition for the extend relationship,
select the extend relationship in the editing pane
(button 1 click) and then bring up its property tab in the
details pane ((button 1 click on the tab). The text of the
condition may be typed in the
field. Long conditions may be split over several lines if
desired. The condition is displayed under the
«extend» label on the diagram.
It is possible to name extend relationships using the
property tab, but this is rarely done, and will not be
displayed on the use case diagram.
The procedure for adding generalizations, is the same
as for adding extend relationships, but using the
generalization icon from the editing pane toolbar (
Since generalization is a directed relationship, the
order of selection matters. The specialized use case should
be selected first (button 1 down) and the generalized
second (button 1 release).
It is also possible to add generalizations using
small “handles” that appear to the top and
bottom of a use case when it is selected. Dragging the
handle at the top to another use case will create a
generalization. The original use case is the specializing
end, and the use case to which the handle was dragged will
be the generalizing end. Dragging into empty space will
create a new use case to be the generalizing end.
Similarly dragging on the bottom handle will create a
generalization in which the original use case is the
Generalization is also permitted between actors,
although its use is beyond the scope of this tutorial.
Unlike use cases there are no generalization handles on
actors, so generalizations must be created using the
It is possible to name generalization relationships
using the property tab, but this is rarely done. If a name
is provided, it will be displayed on the use case
UML has the concept of stereotyping as a way
of extending the basic notation.
It may prove useful for example to model a problem at both the
business level and the engineering level.
It is for this reason that the OMG distinguishes between a PIM
and a PSM.
For both of these we will need use cases, but the use cases
at the business level hold a different sort of information to
those at the engineering level.
Very likely they use different language and notation in their
underlying use case specifications.
Stereotypes are used to label UML
model elements such as use cases, to indicate that they belong to
a certain category. Such labels are shown in guillemots (
« ») above the name of the model element on the
diagram. The UML standard defines a number of standard
stereotypes, and the user may define more stereotypes of his
You will see that ArgoUML has a drop down selector,
Stereotype on every property tab. This is
populated with the standard stereotypes, to which you may add
your own user defined ones.
The details of stereotyping are beyond the scope of
this tutorial. The reference manual (see
Section 16.6, “Stereotype”) documents the support
provided in ArgoUML.
ArgoUML is missing a few of the standard UML
stereotypes. In addition not all model elements will actually
display the stereotype on the diagram. At present this
includes use cases and actors.
ArgoUML has some simple documentation facilities
associated with model elements on a diagram. In general these
should be used only to record the location of material in
documents that can be handled by a mainstream editor or word
processor, not the actual documentation itself.
Documentation for a particular model element is recorded
through the documentation tab in the details pane (the
quadrant of the user screen at the bottom right).
In addition annotation may be added to diagrams using
the text icon on the editing pane toolbar (
The recommendation is that a use case diagram should
use the documentation tab of actors to record information
about the actor, or if the actor is complex to refer to a
separate document that holds information about the
The documentation tab of use cases should record the
location of the use case specification. The information in a
use case specification (for all but the simplest use cases)
is too complex to be placed directly in the tab.
The project should also have a separate vision document
and supplementary requirements specification. A text
annotation on diagrams may be used to refer to these if the
user finds this helpful.
The documentation tab includes a
Deprecated check box. The state of this flag is
not preserved over save and load in the current release of
4.4.7. System Boundary Box
ArgoUML provides a series of tools to provide arbitrary
graphical annotation on diagrams (we have already mentioned
the text tool). These are found at the right hand end of the
editing pane toolbar and are fully documented in the
reference manual (see Chapter 12, The Editing Pane
The rectangle tool can be used to draw the boundary
box. Use the button 2 context-sensitive
Ordering pop-up menu to place it behind everything
else. However there is no way to change its fill color from
the default white. You may therefore prefer to draw the
boundary box as four lines. This is the method used for the
diagrams in this chapter.
The editing pane in ArgoUML has a grid to which
objects snap to aid in drawing. The size of this grid and
its effect may be altered through the
View menu (using
Adjust Grid Snap). This is described
fully in the reference manual (see
Chapter 10, The Menu bar).