METAFOL: Program tactics and logic tactics plus reflection

The goal of this paper is to present a reasoning system, called METAFOL, embodying the features of a self-reeective system, i.e. a system which has a representation of its own code and is able to reason about and, possibly, extend or modify it. These features have been achieved by employing a logical meta-theory, which represents the computation implementing deduction in its object theory. Computation is represented in the meta-theory as logical manipulation of a set of terms, called logic tactics. They are the logical counterpart of a set of programs, called program tactics, implementing deduction in the object theory. The mapping existing between logic tactics and program tactics allows us to synthesize correct programs by reasoning in the meta-theory. It also allows us to implement a reeection mechanism which can be exploited to execute logic tactics and/or compile them into the system code as program tactics.