A formal specification can describe software models which are difficult to program. Transformational methods based on fold/unfold strategies have been proposed to palliate this problem. The objective of applying transformations is to filter out a new version of the specification where recursion may be introduced by a folding step. Among many problems, the "eureka" about when and how to define a new predicate is difficult to find automatically. We propose a new version of the folding rule which decides automatically how to introduce new predicates in a specification. Our method is based on finding similarities between formulas represented as parsing trees and it constitutes an assistance to the complex problem of deriving recursive specifications from non recursive ones.
specification transformation; program synthesis; correctness preservation; program specification