We describe ConcernBASE, a UML-based approach that is an instantiation of the IEEE's Conceptual Framework (Std 1471) for describing software architectures. We show how the approach supports advanced separation of concerns in software architecture by allowing one to identify and define multiple viewpoints, concern spaces and views of an architecture. Our work focuses on integrating the ConcernBASE approach with the Structural Architecture Description Language (SADL) in order to make the verification capabilities of SADL available to those who develop in UML. The result is a UML profile for structural description of software architecture. The paper also presents a prototype tool that supports this UML profile.