INVERSE ENTAILMENT AND PROGOL

This paper firstly provides a re-appraisal of the development of techn iques for inverting deduction, secondly introduces Mode-Directed Inver se Entailment (MDIE) as a generalisation and enhancement of previous a pproaches and thirdly describes an implementation of MDIE in the Progo l system. Progol is implemented in C and available by anonymous ftp. T he re-assessment of previous techniques in terms of inverse implicatio n leads to new results for learning from positive data and inverting i mplication between pairs of clauses.