Some Pathological Message Sequence Charts, and How to Detect Them

Some confusing Message Sequence Charts are identified, that can be considered as syntactically correct, but may lead to ambiguous interpretations. The first kind of MSC identified appears when parallel components of a parallel frame synchronize implicitly to continue an execution. The second case is called non-local choice, and appears when more than one instance is responsible for a choice. Non-local choice has already been studied before. This paper provides an extension of the definitions and corresponding detection algorithms. The third case is confluent MSCs, and appears when concurrency is expressed through a choice.