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          International Workshop on Reduction Strategies 
              in Rewriting and Programming (WRS 2001)

                 held in conjunction with RTA 2001
              in Utrecht, The Netherlands, May 26, 2001

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                         INVITED TALK


    A Survey of Strategies in Program Transformation Systems 

                       by Eelco Visser
                     Universiteit Utrecht
         Institute of Information and Computing Sciences


                          Abstract

   Program transformation is used in a wide range of applications
   including compiler construction, optimization, program
   synthesis, refactoring, software renovation, and reverse
   engineering.  Program transformation entails some kind of
   manipulation of the concrete or abstract syntax tree that
   represents the program.  Implementation of program
   transformation in standard programming paradigms suffers from
   intertwining of logic, i.e., the basic transformation steps,
   and control over the application of basic transformations.
   This intertwining induces programming overhead, makes
   transformations hard to understand and limits reusability.
   The paradigm of transformation strategies overcomes these
   problems by separating logic and control.

   This paper surveys the use of strategies in program
   transformation systems.  After an analysis of the need for
   strategies in program transformation, an analysis of the basic
   elements of a strategy system are discussed and the choices in
   the design of a strategy language are considered. Several
   styles of strategy systems as provided in existing languages,
   from strategy annotations in OBJ to generic strategies in
   Stratego, are then analyzed.  The appendices discuss the
   strategy systems in a number of existing systems.


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