Program restructuring via design-level manipulation

Abstract

A meaning-preserving program restructuring tool can be used by a software engineer to change a program's structure to better support modifications during maintenance. Our implementation of such a tool performs restructuring transformations on code fragments that are selected using a text-based interface. However, a text representation does not represent program structure well because some component relationships that we conceptualize as structure are not readily observable in the program text. For example, structural properties such as module uses or procedure calls are represented by references to names rather than by proximity or direct linkage. Since restructuring is primarily a design-oriented activity, this design information must be readily available. Although the program text may be the wrong representation to manipulate, we still want transformations to directly affect the implementation. To solve both these problems, we use a graphical representation of the program design that displays the program's structure and, unlike visualization tools, permits direct manipulation of the structure to perform transformations on the implementation. We introduce a direct manipulation graphical interface that meets these criteria. We describe its design and implementation, and discuss the special problems of direct-manipulation program restructuring at the design level, and relate it to other approaches for manipulating designs.

This work was supported in part by NSF Grant CCR-9211002.