Deriving tolerant grammars from a base-line grammar

Abstract

C e n t r u m v o o r W i s k u n d e e n I n f o r m a t i c a Software ENgineeringDeriving tolerant grammars from a base-line grammar Deriving tolerant grammars from a base-line grammar ABSTRACT A grammar-based approach to tool development in re-and reverse engineering promises precise structure awareness, but it is problematic in two respects. Firstly, it is a considerable upfront investment to obtain a grammar for a relevant language or cocktail of languages. Existing work on grammar recovery addresses this concern to some extent. Secondly, it is often not feasible to insist on a precise grammar, e.g., when different dialects need to be covered. This calls for tolerant grammars. In this paper, we provide a well-engineered approach to the derivation of tolerant grammars, which is based on previous work on error recovery, fuzzy parsing, and island grammars. The technology of this paper has been used in a complex Cobol restructuring project on several millions of lines of code in different Cobol dialects. Our approach is founded on an approximation relation between a tolerant grammar and a base-line grammar which serves as a point of reference. Thereby, we avoid false positives and false negatives when parsing constructs of interest in a tolerant mode. Our approach accomplishes the effective derivation of a tolerant grammar from the syntactical structure that is relevant for a certain re-or reverse engineering tool. To this end, the productions for the constructs of interest are reused from the base-line grammar together with further productions that are needed for completion. ACM Computing Classification

Toward an engineering discipline for grammarware

“…Examples of adaptive techniques are known in parsing [Barnard 1981;Barnard and Holt 1982;Koppler 1997;Moonen 2001;Klusener and Lämmel 2003;Synytskyy et al 2003]. Clearly, adaptiveness triggers additional concerns such as correctness, as we discuss for parsing in [Klusener and Lämmel 2003]. There is a need for a general methodology for adaptive grammarware.…”

“…That is, if grammatical structure changes in the context of one use case, then these changes can be propagated to other use cases. An example of an operationalised link is the semi-automatic derivation of a tolerant parser from a more strict grammar [Barnard 1981;Barnard and Holt 1982;Klusener and Lämmel 2003]. …”

Natural and Flexible Error Recovery for Generated Modular Language Environments

“…Island grammars [van Deursen and Kuipers 1999;Moonen 2001] have traditionally been used for different reverse and re-engineering tasks. For cases where a baseline grammar is available (i.e., a complete grammar for some dialect of a legacy language), Klusener and Lämmel [2003] present an approach of deriving tolerant grammars. Based on island grammars, these are partial grammars that contain only a subset of the baseline grammar's productions, and are more permissive in nature.…”

Providing rapid feedback in generated modular language environments

“…Island grammars [39,26] have traditionally been used for different reverse and re-engineering tasks. For cases where a baseline grammar is available (i.e., a complete grammar for some dialect of a legacy language), Klusener et al [22] present an approach of deriving tolerant grammars. Based on island grammars, these are partial grammars that contain only a subset of the baseline grammar's productions, and are more permissive in nature.…”