Abstract:

　　Generic language technology and compiler construction techniques are a prerequisite to build analysis and conversion tools that are needed for the re-engineering of large software systems. We argue that generic language technology is a crucial means to do fundamental re-engineering. Furthermore, we address the issue that the application of compiler construction techniques in re-engineering generates new research questions in the field of compiler construction.

　　1 Introduction

　　In 1977, Mathew Hecht wrote in his book [Hec77] on flow analysis of computer programs ``Flow analysis can be used to derive information of use to human beings about a computer program", in fact he was referring to what we nowadays call program understanding or reverse engineering. He further motivated the use of flow analysis by stating that ``some automatic program restructuring may be possible" and that ``perhaps remodularization could be accomodated", techniques that are relevant to restructure and remodularize legacy systems. So, it comes hardly as a surprise that we will argue here that classical compiler construction techniques are extremely useful to aid in re-engineering.

　　Re-engineering is becoming more and more important. There is a constant need for updating and renovating business-critical software systems for many and diverse reasons: business requirements change, technological infrastructure is modernized, governments change laws, or the third millennium approaches, to mention a few. So, in the area of software engineering the subjects of program understanding and system renovation become more and more important. The interest in such subjects originates from the difficulties that one encounters when attempting to maintain large, old, software systems. It is not hard to understand that it is very difficult--if not impossible--to renovate such legacy systems.

　　The purpose of this paper is to show that a substantial part of the technology used in re-engineering often originates from these fields. We want to make researchers in the field of compiler construction and generic language technology aware of the application of their techniques in the field of re-engineering. Furthermore, we will identify topics for further research that are particularly relevant for re-engineering.

　　In [BKV96b] generic language technology is used as a core technology for re-engineering. For more information on the subject of re-engineering we refer to the annotated bibliographies [Arn93] and [BKV96a].

　　2 Reverse Engineering and System Renovation Terminology

　　The term reverse engineering finds its origins in hardware technology and denotes the process of obtaining the specification of complex hardware systems. Now the meaning of this notion has shifted to software. As far as we know there is not (yet) a standard definition of what reverse engineering is but in [CC90] we can read:

　　
``Reverse engineering is the process of analyzing a subject system to identify the system's components and their inter-relationships, and to create representations of the system in another form at higher levels of abstraction.''
According to [CC90] the following six terms characterize system renovation:
Forward engineering.
Reverse engineering.
Redocumentation.
Design recovery.
Restructuring.
Re-engineering (or renovation).
Forward engineering moves from a high-level abstraction and design to a low-level implementation. Reverse engineering can be seen as the inverse process. It can be characterized as analysing a software system in order to, firstly, identify the system components and their interactions, and to, secondly, make representations of the system on a different, possible higher, level of abstraction. This can be seen as a form of decompilation. It may be necessary to move even from assembler (or from the executables) level to a higher level.

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