Dependent types for program understanding

Abstract. Weakly-typed languages such as Cobol often force programmers to represent distinct data abstractions using the same low-level physical type. In this paper, we describe a technique to recover implicitlydefined data abstractions from programs using type inference. We present a novel system of dependent types which we call guarded types, a pathsensitive algorithm for inferring guarded types for Cobol programs, and a semantic characterization of correct guarded typings. The results of our inference technique can be used to enhance program understanding for legacy applications, and to enable a number of type-based program transformations.

Research Issues in the Renovation of Legacy Systems

. The goals of this tutorial are to: (i) give the reader a quick introduction to the field of software renovation as a whole; (ii) show that many techniques from compiler technology and formal methods can be applied; (iii) demonstrate that research should be driven by real-life, industrial, case studies; and (iv) indicate that many challenging problems are still unsolved. During the presentation of this turorial, demonstrations will be given of several of the case studies discussed here. 1 Introduction Software renovation is using tomorrow's technology to bring yesterday's software to the level of today. In this paper, we provide an overview of this research area. We start (in this section) by exploring the need for software renovation. Moreover, we provide definitions of the basic terminology, and pointers to the most important literature. We then proceed to discuss two aspects of software renovation in more detail. In Section 2 we study how we can increase our understanding of..