UML Weekend Crash Course™ - To Parent Directory

56
Saturday Morning
Association notation
A line connecting an actor to a Use Case represents an association, as shown in Figure 5-7.
The association represents the fact that the actor communicates with the Use Case. In fact,
in earlier versions of the UML spec, this was called a Communicates With relationship. This
is the only relationship that exists between an actor and a Use Case. According to the UML
spec, you may specify a directionality arrow on either end of the association line to denote
the direction of the communication. Some associations are unidirectional (for example, the
actor specifies information to the Use Case). Most associations are bidirectional (that is, the
actor accesses the Use Case, and the Use Case provides functionality to the actor). For bidirectional
associations, you may either place an arrowhead on both ends of the association
line, or simply show no arrowheads at all. For simplification, most users tend to show no
arrowheads at all. Most modeling tools provide the option to turn bidirectional arrows on or
off. Just remember that the key is to identify which Use Cases the actors need to access.
These connections will form the basis for the interfaces of the system and subsequent modeling
efforts.
Customer
Withdraw Cash
Update Account
Withdraw Cash
with Overdraft
Protection
Protect Overdraft
Figure 5-7
Association notation for the Use Case diagram
Stereotype notation
The stereotype notation is used throughout the UML, very commonly on Use Case dependencies,
classes, and packages and other elements of the UML known as classifiers. The
standard notation is to enclose the word in guillemets > (French quote marks), as in
the notation below. Stereotypes provide a means to extend the UML without
modifying it. A stereotype functions as a qualifier on a model element, providing more
information about the role of the element without dictating its implementation.
dependency notation
Sometimes one Use Case may need to ask for help from another Use Case. For example, Use
Cases titled Deposit Money and Withdraw Money may not actually update a bank account.
They may delegate the changes to an existing Use Case called Update Account so that
changes are controlled through a single feature that guarantees that all changes are done
correctly.