Checking determinism of XML Schema content models in optimal time
Information Systems
Complexity of Decision Problems for XML Schemas and Chain Regular Expressions
SIAM Journal on Computing
The tractability frontier for NFA minimization
Journal of Computer and System Sciences
Foundations of XML based on logic and automata: a snapshot
FoIKS'12 Proceedings of the 7th international conference on Foundations of Information and Knowledge Systems
LATA'12 Proceedings of the 6th international conference on Language and Automata Theory and Applications
Regular Expressions with Counting: Weak versus Strong Determinism
SIAM Journal on Computing
Almost-linear inclusion for XML regular expression types
ACM Transactions on Database Systems (TODS)
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We study deterministic regular expressions extended with the counting operator. There exist two notions of determinism, strong and weak determinism, which almost coincide for standard regular expressions. This, however, changes dramatically in the presence of counting. In particular, we show that weakly deterministic expressions with counting are exponentially more succinct and strictly more expressive than strongly deterministic ones, even though they still do not capture all regular languages. In addition, we present a finite automaton model with counters, study its properties and investigate the natural extension of the Glushkov construction translating expressions with counting into such counting automata. This translation yields a deterministic automaton if and only if the expression is strongly deterministic. These results then also allow to derive upper bounds for decision problems for strongly deterministic expressions with counting.