This paper presents a method of extraction of the requested information from English sentences which express a certain fact or relations. The restricted input-English sentences are deterministically reduced using the context-free-type production rules presented here, which is constructed tentatively by introducing nonterminal symbol with subscript-variables. And the corresponding logical expressions are constructed. Extractions of requested informations are efficiently performed using the transformation rules between atomic and functional expressions.

In recent years, various formal specification languages have been proposed for validity check of specifications and automatic program generation. However, they are rigorously constructed to be processed by machines and difficult to use. On the other hand, informal languages of conventional notations have been widely used in practice for program specifications but inconvenient to automatic processing by machines. This paper presents a method of transforming between informal specifications and formal specifications. A kind of limited English is introduced as an informal description language of specifications. Specifications written in the limited English are parsed based on a case grammar and transformed into the formal specifications. The formal specifications are also used for various automatic processing such as refinement and program generation. The refined formal specifications can be transformed into the limited English expressions which can be used as comments by the reverse process of the above transformation.