UML provides several kinds of diagrams to model the behavior and structure of a system under development. A consistency problem may arise due to the fact that some aspects of the model may be described by more than one diagram. Hence, it is important that the consistency of the system description should be checked before implementing it.

This paper describes an algorithmic approach to a consistency check between UML Sequence and State diagrams. The algorithm we provide also handles complex State diagrams, e.g. diagrams that include forks, joins, and concurrent composite states. We describe the algorithm in detail, and elaborate on the design decisions made while developing the algorithm. We have implemented BVUML, a tool that assists in automating the validation process.