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Summary: Analysis of Recursive State Machines
Rajeev Alur 1;2 , Kousha Etessami 1 , and Mihalis Yannakakis 1
1 Bell Labs, Murray Hill, NJ
2 Dept. of Comp. and Inf. Science, U. of Pennsylvania
email: falur,kousha,mihalisg@research.belllabs.com
Abstract. Recursive state machines (RSMs) enhance the power of ordi
nary state machines by allowing vertices to correspond either to ordinary
states or to potentially recursive invocations of other state machines.
RSMs can model the control flow in sequential imperative programs
containing recursive procedure calls. They can be viewed as a visual
notation extending Statechartslike hierarchical state machines, where
concurrency is disallowed but recursion is allowed. They are also related
to various models of pushdown systems studied in the verification and
program analysis communities.
After introducing RSMs, we focus on whether statespace analysis can
be performed efficiently for RSMs. We consider the two central problems
for algorithmic analysis and model checking, namely, reachability (is a
target state reachable from initial states) and cycle detection (is there
a reachable cycle containing an accepting state). We show that both
these problems can be solved in time O(n` 2 ) and space O(n`), where
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