Completing One Diagram Before Moving On

Some modelers get stuck because they want to “complete” one diagram before they work on another diagram. For example, a team of developers can easily get fixated on use cases. They complete the use-case diagram and fill out every single use-case description, down to the last alternative scenario. Only then do these developers feel ready to move on to building a class diagram that defines the terminology that crops up in those use-case descriptions. There’s just one problem: They discover that the terms used in the use-case descriptions are inconsistent because various users expressed the same word to mean different concepts and different words mean the same thing. As a result, the single-minded developers must go back to every use-case description and change them, one at a time, to make them consistent with the class diagram.

Tip The work you perform on one diagram can help you with other diagrams. Consider developing your UML diagrams in parallel. For example, when you start your work on use cases, at the same time start building a class diagram as you talk with users. Defining the meaning of the users’ language as you go can help keep your use cases in sync with your class diagram throughout the project.