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classselectumldiagramextend

How to read this UML diagram?

I work in the aviation industry, and I am trying to understand this UML diagram. I did a little bit of UML in college. Can you help me to interpret this diagram?

  • What is the difference between << extend >> and << select >>?
  • What do the big black arrows mean?

UML Diagram

I didn't understand how to read the graph.

Solution

  • «extend»and «select» are stereotypes which were given a certain meaning in the domain of that model. Usually a profile is used to define the sterotypes and their meaning. So the best is you contact the author of the diagram and ask about it. There is no general answer. It looks a bit like these are meant to be requirements.

    The "black arrows" with the lozenge are associations that are given a composite aggregation attribute. The lozenge-side is responsible for the lifetime of the other side. Means it will destroy them when it is destroyed itself.

    Fun note about the «class» (as per comment from Axel Scheithauer from p. 99 of UML 2.5:

    If the default notation is used for a Classifier, a keyword corresponding to the metaclass of the Classifier shall be shown in guillemets above the name. The keywords for each metaclass are listed in Annex C and are specified in the notation for each subclass of Classifier. No keyword is needed to indicate that the metaclass is Class.

    So putting that keyword there is like painting "car" on a car to make it a car, obviously.