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

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Baeten and Bergstra added real time to ACP, a n d i n troduced the notion of integration, which expresses the possibility of an action happening within a time interval. In order to axiomatize this feature, they needed an`uncountable' axiom. This paper deals with pre x integration, and integration is parametrized by conditions, which are inequalities between linear expressions of variables. We present an axiomatization for process terms, and propose a strategy to decide bisimulation equivalence between process terms, by means of this axiomatization.

The way in which a system's software archive is partitioned influences the evolvability of that system. The partition of a software archive is mostly assessed by looking at the static (include, call) relations between the parts. In the literature history information is also taken into account to assess the partition but only pairs of software entities are related. In this paper we describe a novel history-based approach to assess the extent in which a certain partition allows its parts to evolve independently. We use the assumption that a set of software entities which co-evolved often in the past are likely to be modified together in the near future as well. Hence, the elements of such a set should in principle belong to the same part. Our approach, therefore, identifies sets of co-evolving software entities, where each set has elements from more than one part of the archive. We illustrate our approach with a case study of a large software system that evolved during more than a decade, and has over 7 million lines of code.