Extending MSC for reactive systems

Message Sequence Charts (MSC) is a visual language that illustrates the scenarios of system operations, offering user-friendly, easy-to-understand behavioral descriptions. Furthermore, High-level MSC (HMSC) provides composition mechanisms to deal with the complexity of the system. However, for MSC to be used to describe complex reactive systems, there should be ways to deal with reactive behaviors that require the system to respond immediately. In this paper, we propose extensions of MSC to describe complex reactive behaviors in a systematic way. We define the formal semantics of the extended features based on process algebra, as well as the visual and textual syntax. The extensions allow structured, systematic and succinct descriptions of complex reactive behaviors.