In this paper, we consider a model of generalized timed automata (GTA) with
two kinds of clocks, history and future, that can express many timed features
succinctly, including timed automata, event-clock automata with and without
diagonal constraints, and automata with timers.
Our main contribution is a new simulation-based zone algorithm for checking
reachability in this unified model. While such algorithms are known to exist
for timed automata, and have recently been shown for event-clock automata
without diagonal constraints, this is the first result that can handle
event-clock automata with diagonal constraints and automata with timers. We
also provide a prototype implementation for our model and show experimental
results on several benchmarks. To the best of our knowledge, this is the first
effective implementation not just for our unified model, but even just for
automata with timers or for event-clock automata (with predicting clocks)
without going through a costly translation via timed automata. Last but not
least, beyond being interesting in their own right, generalized timed automata
can be used for model-checking event-clock specifications over timed automata
models