Abstract

Quasi-equational logic concerns with a completeness theorem, i. e. a list of general syntactical rules such that, being given a set of graded quasi-equations Q, the closure Cl Q = Qeq Fun Q can be derived from by the given rules. Those rules do exist, because our consideration could be embedded into the logic of first order language. But, we look for special (quasi-equational) rules. Suitable rules were already established for the (non-functorial) case of partial algebras in Definition 3.1.2 of [27], p. 108, and [28], p. 102. (For the case of total algebras, see [35].) So, one has to translate these rules to the (functorial) language of partial theories .Surprisingly enough, partial theories can be replaced up to isomorphisms by partial Dale monoids (cf. Section 3), which, in the total case are ordinary monoids.