Cp. Wirth, Full first-order sequent and tableau calculi with preservation of solutions and the liberalized delta-rule but without Skolemization, LECT N A I, 1761, 2000, pp. 282-297
We present a combination of raising, explicit variable dependency represent
ation, the liberalized delta -rule, and preservation of solutions for first
-order deductive theorem proving. Our main motivation is to pro vide the fo
undation for our work on inductive theorem proving.