UML extensions for capturing timing
Unified Model Language (UML) represents a substantial effort from a large number of methodologists to construct a common means for describing complex systems using the concepts of object-orientation. Since the adoption of UML standard and its new advanced release UML 2.0 this modeling language has been used for the development of a large number of time-critical and resource-critical systems. However, UML is lacking in some key areas that are of particular concern to real-time and embedded systems designers and developers. In particular, the lack of quantifiable notions of time and resources has been an impediment to its broader use and rigorous semantics definition is a mandatory requirement. Fortunately, it was discovered that UML had all the requisite mechanisms for addressing these issues through its extensibility facilities. The link between system execution and time progress may be described in a precise manner, and thus offer support for modelling time dependent behaviour. An active entity was introduced for this purpose to allow the definition of duration constraints between arbitrary events occurring in the system. In addition to the timer object, a clock retrieves the current moment of time. Further extensions allow the identification of syntactically meaningful events of system execution, including the occurrence time and type related information. Furthermore, an operational formalism was defined for expressing assumptions and requirements that involve more complex conditions than the distance between two events. An observer can execute synchronously with a system and monitor its state and events that are occurring. It is used as a language acceptor which may have local memory attributes and their behaviour is described by a state machine. The new UML real-time profile will be evaluated on industrial case studies provided and elaborated by the industrial partners of the OMEGA project. The aim is to incorporate more detailed steps and guidelines on the use of the kernel UML language, especially concerning the proposed time extensions.
