Querying Source Code Using an Algebraic Query Language

Querying and analyzing source code interactively is a critical task in reverse engineering and program understanding. Current source code query systems lack suucient formalism and ooer limited query capabilities. In this paper, we introduce the formal framework of Source Code Algebra (SCA), and outline a source code query system based on it. SCA provides a formal data model for source code, an algebraic expression-based query language, and opportunities for query optimization. An algebraic model of source code addresses the issues of conceptual integrity , expressive power, and performance of a source code query system within a uniied framework. 1 Overview The answers are in the source code. Mark Weiser, in Source Code 28]. Software reverse engineering, code re-engineering, and program understanding have begun to emerge as the latest challenges in the eld of software engineering. Interest in these areas stems from the need to maintain extremely large, old, and unwieldy software systems (also called legacy systems), which for reasons of economics cannot be thrown away and rewritten. An early conclusion in this area of study is that a complete automation of the reverse engineering process is not feasible 8]. It is felt that the reverse engineering of real systems must involve substantial human participation. This acceptance, in turn, leads to a critical need for software tools that can assist or support the human reverse engineers in their task. An essential component in a reverse engineer's toolkit must be a tool to query source code interactively. It is widely accepted that in legacy systems, the source code is the only true documentation of program structure and behavior 20, 24]. Recovering the design of a such a system will necessarily involve close and careful scrutiny of its source code. The need for source code query tools has been articulated by Biggerstaa in terms of a \conceptual grep" 2]. The purpose of a source code querying tool is to help human reverse engineers indulge in plausible reasoning 2] or domain bridging 3] | an iterative process of guesswork and veriication that leads them to a better understanding of what the source code is doing. A reverse engineer may pose queries pertaining to diierent views of the source code. One view is based on composition relationships. This includes queries related to global structural information, e.g., composition relations between program entities such as les, functions, variables, types, etc. Queries can also be based on statement-level …