Comments on: Uncovering Requirements With UML Class Diagrams Part 4 http://tynerblain.com/blog/2008/03/17/requirements-class-diagrams-4/ Software product success. Tue, 22 May 2012 20:46:27 +0000 hourly 1 http://wordpress.org/?v=3.0.4 By: Yanic http://tynerblain.com/blog/2008/03/17/requirements-class-diagrams-4/comment-page-1/#comment-332895 Yanic Fri, 21 Mar 2008 01:05:43 +0000 http://tynerblain.com/blog/2008/03/17/requirements-class-diagrams-4/#comment-332895 I'd like to comment on what you did to your model in the 'More complex class diagram' step. Specifically : you model the same association on both the super class and sub class (for example 'is written by' on both Agreement and FixedAgreement). Presumably to override/refine/specialize the inherited association. I know it is valid UML, but I find it a confusing and ambiguous approach. How about using one of the alternatives below? 1) give each class its own association (but then you lose the connection that they're the same thing really) 2) only model the one on the superclass and constrain the possible links for subclass instances (but then you lose substitutability) 3) create a separate class for the association, e.g. Authorship, where you constrain the possible combinations of Agreement and Agent kinds. If it were up to me, I'd go with #3. Best regards, Yanic I’d like to comment on what you did to your model in the ‘More complex class diagram’ step.

Specifically : you model the same association on both the super class and sub class (for example ‘is written by’ on both Agreement and FixedAgreement). Presumably to override/refine/specialize the inherited association.

I know it is valid UML, but I find it a confusing and ambiguous approach. How about using one of the alternatives below?

1) give each class its own association (but then you lose the connection that they’re the same thing really)

2) only model the one on the superclass and constrain the possible links for subclass instances (but then you lose substitutability)

3) create a separate class for the association, e.g. Authorship, where you constrain the possible combinations of Agreement and Agent kinds.

If it were up to me, I’d go with #3.

Best regards,
Yanic

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