11.6. Revised SRS Class Diagram

Going back to the SRS class diagram that we produced in Chapter 10, let's reflect all the new insights—some behavioral, some structural—that we gained from analyzing one scenario/sequence diagram (see Figure 11-14).

Figure 11.14. Revised SRS class diagram

Note that we decided not to reflect the ConfirmSeatAvailability() "housekeeping" method at this time because we suspect that it will be a private method and therefore don't want to clutter our diagram. The decision of whether to reflect private methods on a class diagram—or to reflect any member of a class—is up to the modeler because the purpose of the diagram is to communicate, and too much detail can actually lessen a diagram's effectiveness in this regard.

UML also provides notation to indicate the access (public/protected/private) given to each member of a class by placing a symbol to the left of the member name. A + symbol indicates public access, a – symbol means private access, and a # symbol indicates protected access. Because we haven't yet mapped out what the access of the SRS class members will be, we'll omit this notation for now.

We must remember to update the SRS data dictionary any time we add classes, fields, relationships, or methods to our model. Here's a suggested format for how we might want to describe a method in the dictionary:

Method

Enroll

Defined for class

Section

Header

bool Enroll(Student s)

Description:

This method enrolls the designated person in the section, unless (a) the section is already full, (b) the student's plan of study doesn't call for this course, or (c) the student hasn't met the prerequisites. It returns a bool value to indicate success (true) or failure (false) of the enrollment.