Today I'd like to share a small video with you which raises an important issue: UML Model Validation. Being an extremely complex language without proper understanding of the rules and constraints of the UML Model it is easily possible to create invalid UML models. That is why there are standard documents and also a certification program for UML to help people look under the hood of the diagrams.
And here is the video by a tool vendor (*) to solve the problem of model validation
http://www.download-omondo.com/model_validation.swf (I took it from a LinkedIn discussion)
I love the part in the middle of the video when the model is actually validated. In UML terms the error message is absolutely correct. In terms of human readable error messages there seems to be a problem, as illustrated by the video (you need to have sound).
(*) Please note that I do not have any kind of affifilation with the vendor, nor know the tool particularily well. Having said that I do not want to say it is a bad tool, I also do not want to endorse it. The problem is very common among UML tools and usually they tend to be decreasingly useful when the constraints to be validated get more complicated.