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classoopumlclass-diagram

Is this UML class diagram correct?

I have been struggling to get my system into a class diagram. I tend to make relationship mistakes by thinking too much in database structure. I have a class diagram:

enter image description here

So to explain the situation I need:

The employee part:

  • An employee can be assigned to 0 or more projects by a project phase

The project part:

  • A project is of a certain type (I can get confused with if a project HAS or IS of a certain type).
  • A project type consists of 1 or more project phases
  • A project phase IS of a certain phase

To explain what the system must do:

An employee can be assigned to a certain phase of a project. The project should be of a certain type and that type consists of certain project phases. The project phase is a certain phase.

Because an employee needs to see all of his current projects etc I made a link to employee and project too. I don't know if this is correct or that it is the project phase it's responsibility to provide the right project to the employee.

Solution

  • I think this is the class diagram that suits your requirements:

    enter image description here

    I have modeled composition associations between Project/ProjectPhase and between ProjectType/Phase, because a Project consists of ProjectPhases and ProjectPhases cannot exist without their Projects and the same is true for ProjectType/Phase.

    Employees and ProjectPhases neither have a part-of relationship nor an existency dependency, hence a compositions association is not appropriate here.

    In my diagram, an Employee is implicitly assigned to Projects via ProjectPhases, but if you want to stress the relationship between Employees and Projects, you may very well draw an association between these classes explicitly.