Decidability of EDT0L structural equivalence

Decidability of Split Equivalence

We show that the following problem is decidable: given expressions E1 and E2 constructed from variables by the regular operations and shuffle, is the identity E1 = E2 true for all instantiations of its variables by strings? Our proof uses the notations developed in the causal approach to concurrency. As a byproduct we obtain decidability of similar equivalence for other formalisms. In particula...

Decidability of DPDA equivalence

A proof of decidability of equivalence between deterministic pushdown automata is presented using a mixture of methods developed in concurrency and language theory. The technique appeals to a tableau proof system for equivalence of configurations of strict deterministic grammars.

An Introduction to Decidability of DPDA Equivalence

Decidability of Bisimulation Equivalence for Pushdown Processes

We show that bisimulation equivalence is decidable for pushdown automata without ǫ-transitions.

Decidability of Equivalence of Aggregate Count-Distinct Queries

We address the problem of equivalence of count-distinct aggregate queries, prove that the problem is decidable, and can be decided in the third level of Polynomial hierarchy. We introduce the notion of core for conjunctive queries with comparisons as an extension of the classical notion for relational queries, and prove that the existence of isomorphism among cores of queries is a sufficient an...