Information Technology Reference
In-Depth Information
Fig. 3.3
Example of an actor
Make Appointment
communication
Actor
use case
for initiating user events within a software system. Actors, like objects, have
unique names so that they can be identified as entities within the system.
Figures
3.3
and
3.4
illustrate the relationship that an actor has with a system. The
oval labeled
Make Appointment
represents a use case that describes the sys-
tems response to an externally initiated event (use cases will be discussed in
greater detail later in the chapter). The event in question is denoted by the line
linking the use case to the actor itself, represented by a stick figure. In this
example, the actor, a
patient
, is using the system to make an appointment. In
the next example, Fig.
3.4
, we are shown a situation in which multiple actors
interact with the system. This diagram describes a point-of-sale checkout system in
a convenience store. The
Sales_Clerk
interacts with the system to begin the
interaction. In this case, imagine the
Customer
has elected to pay by debit card.
The
Customer
must now interact with the system on its own to enter in a
personal identification number. The actor-use case standard allows both members
of a software engineering team and the client to visualize and discuss the external
interactions that a software system intends to handle.
Fig. 3.4 Example of
multiple user situation
Clerk
Process Sale
Cust-
