Third-class associations in interfaces

[Javier]

I'm modeling a telephony framework (JTAPI) that declares an association class at the level of interfaces.

IF I declare three Interfaces named Address, Call and Connection, and associate Address and Call, I don't have a problem.  I can manipulate the association correctly.  However, IF I want to associate the Connection as a third-class association, I can't.  EA does not offer me the possibility.

It is only when I change them to a Class that I can do it.

The workaround that I did is to turn them into a Class with a stereotype of <<interface>>.

My understanding is that this is not a limitation in UML, is it?--coupled by the fact that I can do it in Rose, but Rose does not differentiate between Interface and Class as EA does, except in the stereotypes.

So...is this a bug, or a feature?