Finite-automaton decision procedures
A DFA's language is empty iff no accepting state is reachable from its start.
Key knowledge
A DFA's language is empty iff no accepting state is reachable from its start. Two DFAs are equivalent iff their product automaton's symmetric-difference language is empty. Product-state accepting rules also construct regular intersections and unions; swapping accepting/nonaccepting states complements a complete DFA.
Conditions and scope
- Automata have a common finite alphabet and total transitions; add a rejecting sink when needed.
- The analogous grammar equivalence problem is not decided by this construction.
Sources · 1
References
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Evidence and review
Lecture 7 slides 5–6, reachability and symmetric-difference constructions.
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Entry details
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