In this step we shall define the methods of the classes that were discovered during the previous step. In this step we define the behaviour of our system. In other words, we go for the following targets [Rosenberg, 1999]:
1. Distribution of behaviour to boundary, control and entity objects.
2. Identification of the interactions between the objects of each use case
3. Complete the distribution of the methods to the classes.
The methodology that we follow for the creation of sequence diagrams is summarized as follows:
The fourth step is the most difficult one and we should make a decision as to which methods correspond to which objects.