We consider the problem of grammatical inference (GI) for classes of structured documents like summaries, dictionaries, bibliographic data basis, encyclopaedias and so on. The inference is based on examples of individual sample of these documents. In this paper, we present an algebraic framework of the GI in which rewrite rules will define the process of generalisation. The implementation algorithm discussed here is used in a document handling project in which paper documents are typographically tagged and then recognised. One of the current applications in this project is to translate paper documents into machine readable form