A Language for Proofs Using Galois Connections and Fork Algebras

Galois is a domain specific language supported by the Galculator interactive proof-assistant prototype. Galculator uses an equational approach based on Galois connections with indirect equality as an additional inference rule. Galois allows for the specification of different theories in a point-free style by using fork algebras, an extension of relation algebras with expressive power of first-order logic. The language offers sub-languages to derive proof rules from Galois connections, to express proof tactics, and to organize axioms and theorems into modular definitions. In this paper, we describe how the algebraic theory underlying the proof-method drives the design of the Galois language. We provide the syntax and semantics of important fragments of Galois and show how they are hierarchically combined into a complete language.