[Uml-devel] What the hell are uni-associations?

[Jonathan Riddell]

On Wed, Feb 04, 2004 at 03:51:53PM -0500, Brian Thomas wrote:

> 	I'm trying to bug fix the association/code generation aspects of umbrello
> 	and I realized that I had no real definition of what these things are
> 	(uni-associations). The best information I can find at www.omg.org
> 	is from the section on OCL in the UML 2.0 spec, but thats ahead of
> 	where we are, no?
> 
> 	It would appear to me (using old UML 1.4 spec, granted) that these things are
> 	a type of association invented for Umbrello (only), and are meant to imply
> 	aggregations, wherein one end of the association is "navigable" (e.g. 
> 	has an arrow pointing to the classifier). The role name is taken from the
> 	class to which it points, and the multiplicity, is "1".

It's not just an invention of Umbrello.  From the UML 1.5 spec.

3.43.2.4 navigability 

       An arrow may be attached to the end of the path
       to indicate that navigation is supported toward the classifier
       attached to the arrow. Arrows may be attached to zero, one, or
       two ends of the path. To be totally explicit, arrows may be
       shown whenever navigation is supported in a given direction. In
       practice, it is often convenient to suppress some of the arrows
       and just show exceptional situations. See Section 3.22.3,
       Presentation Options,  on page 3-36 for details.


Just what navigability means doesn't seem to be defined.  

A-->B

I take to mean that A knows about B but B doesn't know about A.  

I'd be impressed if anyone knows the difference between that and
composition, aggregation or depenency.  I understand them to be
essentially the same.

Jonathan Riddell