Relationships and Operation Signatures

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The signature of an operation may indicate a relationship. If the class for an argument of an operation or the return from an operation is a fundamental class such as a String, the relationship typically is not shown on a diagram. For other classes (i.e., nonfundamental classes) the relationship typically is displayed on one or more class diagrams. For example, the two inputs to the setProfessor() operation of the Course class are professor ( Professor class) and course offering (CourseOffering class). This implies that relationships exist between:

• Course and Professor

• Course and CourseOffering

Relationships based on operation signatures initially are modeled as associations that may be refined into dependency relationships as the design of the system matures. Refinement is covered in Chapter 12. Package relationships should also be reviewed as relationships based on operation signatures are added to the model. For example, we have now added a relationship between the Course class and the Professor class. This implies that there is a dependency relationship between the University Artifacts package and the People package.

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