This volume contains selected papers from LOPSTR 2003, the 13th Inter- tional Symposium on Logic-Based Program Synthesis and Transformation. The LOPSTR series is devoted to research in logic-based program development. P- ticular topics of interest are speci?cation, synthesis, veri?cation, transformation, specialization, analysis, optimization, composition, reuse, component-based so- ware development, agent-based software development, software architectures, design patterns and frameworks, program re?nement and logics for re?nement, proofs as programs, and applications and tools. LOPSTR 2003 took place at the University of Uppsala from August 25 to August 27 as part of PLI 2003 (Principles, Logics, and Implementations of High- Level Programming Languages). PLI was an ACM-organized confederation of conferences and workshops with ICFP 2003 (ACM-SIGPLAN International C- ference on Functional Programming) and PPDP 2003 (ACM-SIGPLAN Inter- tional Conference on Principles and Practice of Declarative Programming) as the main events. The LOPSTR community pro?ted from the shared lectures of the invited speakers, and the active scienti?c discussions enabled by the co-location. LOPSTR 2003 was the thirteenth in a series of events. Past events were held in Manchester, UK (1991, 1992, 1998), Louvain-la-Neuve, Belgium (1993), Pisa, Italy (1994), Arnhem, The Netherlands (1995), Stockholm, Sweden (1996), L- ven, Belgium (1997), Venice, Italy (1999), London, UK (2000), Paphos, Cyprus (2001), and Madrid, Spain (2002).

1 The tenth anniversary of the LOPSTR symposium provided the incentive for this volume. LOPSTR started in 1991 as a workshop on logic program synthesis and transformation, but later it broadened its scope to logic-based program development in general, that is, program development in computational logic, and hence the title of this volume. The motivating force behind LOPSTR has been the belief that declarative paradigms such as logic programming are better suited to program development tasks than traditional non-declarative ones such as the imperative paradigm. Speci?cation, synthesis, transformation or specialization, analysis, debugging and veri?cation can all be given logical foundations, thus providing a unifying framework for the whole development process. In the past 10 years or so, such a theoretical framework has indeed begun to emerge. Even tools have been implemented for analysis, veri?cation and speci- ization. However, itisfairtosaythatsofarthefocushaslargelybeenonprogrammi- in-the-small. So the future challenge is to apply or extend these techniques to programming-in-the-large, in order to tackle software engineering in the real world. Returning to this volume, our aim is to present a collection of papers that re?ect signi?cant research e?orts over the past 10 years. These papers cover the wholedevelopmentprocess: speci?cation, synthesis, analysis, transformationand specialization, as well as semantics and sys

This volume contains the proceedings of the Fifth International Symposium onProgramming Language Implementation and Logic Programming (PLILP '93), held in Tallinn, Estonia, in August 1993. The series of PLILP symposiums was established to promote contacts and information exchange among scientists who share common interests in declarative programming techniques, logic programming, and programming languages imnplementation. Researchers from the fields of algorithmic programming languages as well as logic, functional, object-oriented, and constraint programming constitute the audience of PLILP. The volume contains three invited talks and 24 selected contributed papers grouped intoparts on: integration of different paradigms, constraint programming, staticanalysis and abstract interpretation, grammars, narrowing, parallelism, and implementation techniques. The volume closes with six abstracts of systems demonstrations and posters.

This volume contains the papers accepted for presentation at the Fourth International Symposium on Programming Language Implementation and Logic Programming (PLILP '92) held in Leuven, Belgium, August 26-28, 1992. Theaim of the symposium was to explore new declarative concepts, methods and techniques relevant for implementation of all kinds of programming languages, whether algorithmic or declarative. The symposium gathered researchers from the fields of algorithmic programming languages as well as logic, functional, and object-oriented programming. The topics discussed in the volume include: - Declarative implementation techniques; - Implementation of declarative concepts and modules; - Compiler specification and construction; - Program transformation; - Programming environments for declarative languages; - Amalgamation of logic programming with algorithmic, functional, or object-oriented techniques; - Executable specification.