Building and executing proof strategies in a formal metatheory

This paper describes how "safe" proof strategies are represented and executed in the interactive theorem prover GETFOL. A formal metatheory (MT) describes and allows to reason about object level inference. A class of MT terms, called logic, tactics, is used to represent proof strategies. The semantic attachment facility and the evaluation mechanism of the GETFOL system have been used to provide the procedural interpretation of logic tactics. The execution of logic tactics is then proved to be "safe" under the termination condition. The implementation within the GETFOL system is described and the synthesis of a logic tactic implementing a normalizer in negative normal form is presented as a case study.