1. Introduction
Model-based conformance testing of real-time systems has attracted increasing research interests in recent years. A large proportion of these work employ Timed Automata (TA) or its variants to model the systems. Among them some make the assumptions that the system TA model is output-urgent and has isolated outputs [14] [7]. “Output-urgent” means that if the system can produce an output, then it should produce the output immediately. “Isolated output” means that at any moment in time if the system can produce an output, then it cannot accept inputs and cannot produce a different output. These assumptions on TA contribute to the testability property [14]. However, in many cases they are unnecessarily strong.