Purpose

Steps

Heuristics

Artifacts

   The relationships diagrams capture the static relationships that exist between the participants of the problem analysis model. The relationship diagrams represent the static structure of the system. The static structure of the participants is derived from the participant RC cards, which is indirectly derived from the behaviors described by the use cases.

1. • Aggregation relationships are characterized by the “has-a” relationship. Aggregation is a weak form of coupling, therefore this relationship is further characterized by the independence of the two participants in the relationship. That is, if the relationship is removed, the participants are still viable entities.
   

2. • Composition relationships are also characterized by the “has-a” relationship. However, participants in the composition relationship are no longer viable participants if separated. Composition infers lifecycle dependency.
   

3. • Inheritance represent the “is-a” relationship. If two participants are in an inheritance relationship, one can be substituted for the other without affecting the behavior in which they participate (the Liskov Substitution Principle.)

Composition / Aggregation Class Diagram (Example)

Inheritance Class Diagram (Example)

1. 1. Begin with two blank UML class diagrams. We suggest one for aggregation / composition relationships, and another for inheritance relationships.
   

2. 2. Add an appropriate title and date / version to the diagram.
   

3. 3. Referring to the participant RC cards, identify any collaborations in the knowledge section and transfer the two participants to the blank diagram. Add a relationship between the two participants using the appropriate notation for aggregation or composition. Note the cardinality of the relationship.
   

4. 4. Based on your knowledge of the problem domain, identify other static relationships of interest and add them to the diagram.
   

5. 5. If there are any classification relationships, add them to the inheritance diagram.