hasa in UML

UML does not, in fact, has a direct notion of aggregation.

There are three concepts that might be pressed into the service of 
aggregation:

Association (3.41 and following)
Composite Object (3.40)
Collaboration diagrams (3.65 and following)

Association is simply a relationship. There is no additional semantics 
built-in. We can define our own form of association called has-a (but 
we are trying to avoid that right?)

"A composite object represents a high-level object made of tightly 
bound parts. This is an instance of a composite class, which implies 
the composition aggregation between the class and its parts. A 
composite object is similar to (but simpler and more restricted than) a 
collaboration; ..."

I do not think that this meets our needs. It is not accurate to say 
that a service is composed of X + an identifier.

Collaborations on the other hand are not what is going on either:

"A collaboration is used for describing the realization of an Operation 
or Classifier."

Frank

On Friday, May 30, 2003, at 02:10  PM, Cutler, Roger (RogerCutler) 
wrote:

>
> Well, that's progress of a sort.  Now what do "generalization" and
> "aggregation" mean, and how does this differ from the current
> definition?
>