This article analyses and critically assess some UML modeling solutions with observations regarding types, interfaces and classifiers, and problems of associations semantics and notation. Well formedness rules, their format and role are also analyzed. Use case modeling is assessed through their role in eliciting user’s requirements, and dealing with the functionality of the system. Some examples show the potential danger of using use-cases as a replacement for functional decomposition. This could result in some important abstractions in the system not being revealed and not seeing use cases as a representation of collective functionality where their components act as collaborations between objects.