TURTLE: a real-time UML profile supported by a formal validation toolkit

We present a UML 1.5 profile named TURTLE (Timed UML and RT-LOTOS Environment) endowed with a formal semantics given in terms of RT-LOTOS. TURTLE relies on UML´s extensibility mechanisms to enhance class and activity diagrams. Class diagrams are extended with specialized classes named Tclasses, which communicate and synchronize through gates. Also, associations between Tclasses are attributed by a composition operator (Parallel, Synchro, Invocation, Sequence, or Preemption) which provides them with a formal semantics. TURTLE extends UML activity diagrams with synchronization actions and temporal operators (deterministic delay, nondeterministic delay, time-limited offer, and time-capture). The real-time dimension of TURTLE has been further improved by the addition of two composition operators, periodic and suspend, as well as suspendable delay, latency, and time-limited offer operators at the activity diagram level. Core characteristics of TURLE are supported by TTool - the TURTLE toolkit - which includes a diagram editor, a RT-LOTOS code generator and a result analyzer. The toolkit reuses RTL, a RT-LOTOS validation tool offering debug-oriented simulation and exhaustive analysis. TTool hides RT-LOTOS to the end-user and allows him/her to directly check TURTLE modeling against logical errors and timing inconsistencies. Besides the foundations of the TURTLE profile, this paper also discusses its application in the context of space-based embedded software.