Attribute Multiplicity

  • Dina

    Dina - 2012-02-06

    I have some questions regarding the tool modeling.

    Q1: Are the class attributes optional by default or not? If not, How can I indicate that they are optional?
           For example, I want to model class Book which has a "year" as a normal attribute,  an "ISBN" as an optional attribute, and another one called GS1 which is optional; it doesn't exist except if the ISBN number and satisfies the condition that the "year" is greater than or equal 2007.

    Q2: I have a class book and I want to say that it is either edited by an Editor or authored by an author but it can't be both (i.e. an XOR relationship). How can I write this type of constraint using OCL in your tool?

    Thanks a lot


  • Lars Hamann

    Lars Hamann - 2012-02-07


    A1: Attributes are optional by default. To make them mandantory you need to specify an invariant.

    context Book inv: self.year.isDefined()

    A2: Given the association ends "author" and "editor" you can write:

    context Book inv authorExcludesEditor: implies self.editor.isUndefined()

    Best regards!


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