Theorem Proving and Proof Verification in the System SAD

In this paper, the current state of the System for Automated Deduction, SAD, is described briefly. The system may be considered as the modern vision of the Evidence Algorithm programme advanced by Academician V. Glushkov in early 1970s. V. Glushkov proposed to make investigation simultaneously into formalized languages for presenting mathematical texts in the form most appropriate for a user, formalization and evolutionary development of computer-made proof step, information environment having an influence on the evidence of a proof step, and man-assisted search for a proof. In this connection, SAD supports a number of formal languages for representing and processing mathematical knowledge along with the formal language ForTheL as their top representative, uses a sequent formalism developed for constructing an efficient technique of proof search within the signature of an initial theory, and gives a new way to organize the information environment for sharing mathematical knowledge among various computer services. The system SAD can be used to solve large variety of theorem proving problems including: establishing of the deducibility of sequents in first-order classical logic, theorem proving in ForTheL-environment, verifying correctness of self-contained ForTheL-texts, solving problems taken from the online library TPTP. A number of examples is given for illustrating the mathematical knowledge processing implemented in SAD.