Supporting the restructuring of data abstractions through manipulation of a program visualization

Abstract

With a meaning-preserving restructuring tool, a software engineer can change a program's structure to ease future modifications. However, deciding how to restructure the program requires a global understanding of the program's structure, which cannot be derived easily by directly inspecting the source code. We describe a manipulable program visualization—the star diagram —that supports the restructuring task of encapsulating a global data structure. The star diagram graphically displays information pertinent to encapsulation, and direct manipulation of the diagram causes the underlying program to be restructured. The visualization compactly presents all statements in the program that use the given global data structure, helping the programmer to choose the functions that completely encapsulate it. Additionally, the visualization elides code unrelated to the data structure and to the task and collapses similar expressions to help the programmer identify frequently occurring code fragments and manipulate them together. The visualization is mapped directly to the program text, so manipulation of the visualization also restructures the program. We present the star diagram concept and describe an implementation of the star diagram built upon a meaning-preserving restructuring tool for Scheme. We also describe our creation of star diagram generators for C programs, and we test the scalability of the star diagram using large C and MUMPS programs.