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Home » Modeling » UML2 » Navigability Semantics of Associations
Navigability Semantics of Associations [message #625894] Sat, 12 January 2008 13:05
Felix Dorner is currently offline Felix DornerFriend
Messages: 676
Registered: July 2009
Senior Member
Hello,

I try to understand the navigability semantics of associations.
Because I am very insure if my below statements are correct, please
correct them if neccessary:

Suppose I have a Class Book and a Class Author.

Task 1 - Bidirectional Navigability:
------------------------------------

I'd like to have an association book_author between the two
Classes which is navigable in both directions:

a. Create an Association book_author.

b. Inside the Author class I create an owned Property "books" of type
Book set its Association Property to "book_author"

c. Inside the Book class I create an owned Property "author" of type
Author and also set its Association Property to "book_author".


Task 2 - Unidirectional Navigability
-------------------------------------

I'd like to restrict navigability, only Author->Book should be
possible.

a. I change the owner of the "author" property from Book to the
Association "book_author".

Conclusion: Since the "author" end is now owned by the Association
it is not navigable from the opposite end "book" anymore.


Task 3 - Restore Navigability by making Use of an Association's
"navigableOwnedEnd" property:
------------------------------------------------------------ ----

If I also add the "author" end to the "ownedNavigableEnds"
property of the Association, navigation from "book" to "author" would
be possible again.

Now I can't see any semantic difference between an end owned by an
opposite end's class and that end owned by the Association and part of
its "ownedNavigableEnd" property. Do I miss something?

Task 4 - Make the Association not navigable at all
--------------------------------------------------

Make all ends owned by the Association. Why should one need this?



Thanks for a discussion.
Felix
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