So you'll find that the UML in one case tools doesn't mean the same as the UML in another. CASE tools talk about their ability to check your diagrams for you, to prevent you from making mistakes. They see it as a feature, but I'm not so sure. I know what I want to do, and I find it very irritating when a CASE tools doesn't let me do something I need. People see it as a boon for less experienced developers, but I think that a good review process is far more valuable than mechanical checking.
Tools miss the subtleties of communication.
So don't let CASE tools be the arbiter of what you draw. Your brain can beat a CASE tools any day.