We consider the representable equational theory of binary relations, in a language expressing composition, converse, and lattice operations. By working directly with a presentation of relation expressions as graphs we are able to define a notion of reduction which is confluent and strongly normalizing and induces a notion of computable normal form for terms. This notion of reduction thus leads ...

We study homomorphisms of propositional formulas in CNF generalizing symmetries considered by Krishnamurthy. If φ : H → F is a homomorphism, then unsatisfiability of H implies unsatisfiability of F . Homomorphisms from F to a subset F ′ of F (endomorphisms) are of special interest, since in such case F and F ′ are satisfiability-equivalent. We show that smallest subsets F ′ of a formula F for w...