A Constructor-based Approach for Positive/negative-conditional Equational Speciications

We present a constructor-based approach for assigning appropriate semantics to algebraic speciications given by nite sets of positive/negative-conditional equations. Under the assumption of con-uence of the reduction relation we deene, the factor algebra of the ground term algebra modulo the congruence of this reduction relation is a minimal model which is (beyond that) the minimum of all models that do not identify more constructor ground terms than necessary.