Model Reduction of Discrete Real-time Systems
نویسنده
چکیده
In many Discrete Event Systems DES both state and event information are of im portance to the systems designer To obtain compositionally consistent hierarchical models of systems the behavior of Discrete Event Systems with unobservable tran sitions and state output maps is considered Observers for deterministic DES are generalized to nondeterministic DES and characterized using the join semilattice of compatible partitions of a transition system This characterization points to e cient algorithms for computing both strong and weak state event observers as solutions to the Relational Coarsest Partition problem RCP The strong and weak observation equivalences of Milner are shown to be special cases of our observers under the trivial constant state output map The state event equivalence based upon the observers is shown to be a congruence for a parallel composition operator allowing the replacement of modules by their quotient systems Logics such as Ostro s RTTL allow for the speci cation and veri cation of a system s state event behavior To make realistic problems amenable to analysis a designer must typically decompose the system into subsystems modules and use al gebraic abstraction quotient systems to obtain hierarchical system models that pre serve the properties to be veri ed In this thesis we use state event observational equivalence to perform compositionally consistent model reduction for a subclass of formulas of state event linear temporal logics with particular attention to a discrete time temporal logic that is a simpli cation of RTTL The reduction technique allows limited use of immediate operators In the process we develop a method of specify ing modules input output behavior by de ning observable satisfaction for RTTL style temporal logics The results are applied to the shut down system of a nuclear reactor
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