As computer science enters the new millennium, methods and languages for reasoning with constraints have come to play an important role, with both t- oretical advances and practical applications. Constraints have emerged as the basis of a representational and computational paradigm that draws from many disciplinesandcanbebroughttobearonmanyproblemdomains,includingar- ?cial intelligence, databases, and combinatorial optimization. The conference is concerned with all aspects of computing with constraints including algorithms, applications, environments, languages, models and systems. The Sixth InternationalConference on Principles and Practiceof Constraint Programming (CP2000) continues to provide an international forum for p- senting and discussing state-of-the-art research and applications involving c- straints.Afterafewannualworkshops,CP'95tookplaceinCassis,France;CP'96 in Cambridge, USA; CP'97 in Schloss Hagenberg, Austria; CP'98 in Pisa, Italy and CP'99 in Alexandria, USA. This year the conference is held in Singapore, from 18 through 21 September 2000. This volume comprises the papers that were accepted for presentation at CP2000.From the 101 papersthat were submitted, 31 papers wereaccepted for presentation in the plenary session and 13 papers were selected as posters and have a short version (? ve pages) in this volume. All papers were subjected to rigorous review three program committee members (or their designated revi- ers) refereed each paper. Decisions were reached following discussions among reviewers and, in some instances, by e-mail consultation of the entire program committee.Ibelievethereaderwill?ndthesearticlestobeofthehighestquality, representing a signi?cant contribution to the ?eld.

Table of Contents:
Invited Papers.- Constraint-Based Agents: The ABC’s of CBA’s.- Constraints for Interactive Graphical Applications.- Meta-complexity Theorems: Talk Abstract.- Regular Papers.- Automatic Generation of Propagation Rules for Finite Domains.- Extending Forward Checking.- Global Constraints as Graph Properties on a Structured Network of Elementary Constraints of the Same Type.- Universally Quantified Interval Constraints.- Constraint Propagation for Soft Constraints: Generalization and Termination Conditions.- Constraints Inference Channels and Secure Databases.- Refinements and Independence: A Simple Method for Identifying Tractable Disjunctive Constraints.- A Language for Audiovisual Template Specification and Recognition.- Random 3-SAT: The Plot Thickens.- New Tractable Classes from Old.- Expressiveness of Full First Order Constraints in the Algebra of Finite or Infinite Trees.- Cutting Planes in Constraint Programming: An Hybrid Approach.- A Constraint-Based Framework for Prototyping Distributed Virtual Applications.- A Scalable Linear Constraint Solver for User Interface Construction.- A Constraint Programming Approach for Solving Rigid Geometric Systems.- Maintaining Arc-Consistency within Dynamic Backtracking.- New Search Heuristics for Max-CSP.- Analysis of Random Noise and Random Walk Algorithms for Satisfiability Testing.- Boosting Search with Variable Elimination.- Faster Algorithms for Bound-Consistency of the Sortedness and the Alldifferent Constraint.- Practical Investigation of Constraints with Graph Views.- A Hybrid Search Architecture Applied to Hard Random 3-SAT and Low-Autocorrelation Binary Sequences.- Singleton Consistencies.- Linear Formulation of Constraint Programming Models and Hybrid Solvers.- A Global Constraint Combining a Sum Constraint andDifference Constraints.- Efficient Querying of Periodic Spatiotemporal Objects.- Arc Consistency for Soft Constraints.- Optimal Anytime Constrained Simulated Annealing for Constrained Global Optimization.- SAT v CSP.- Instruction Scheduling with Timing Constraints on a Single RISC Processor with 0/1 Latencies.- Arc Consistency on n-ary Monotonic and Linear Constraints.- Poster Papers.- Some Observations on Durations, Scheduling and Allen’s Algebra.- Using Randomization and Learning to Solve Hard Real-World Instances of Satisfiability.- Finding Minimal Unsatisfiable Subformulae in Satisfiability Instances.- Branching Constraint Satisfaction Problems for Solutions Robust under Likely Changes.- Constraint Propagation: Between Abstract Models and ad hoc Strategies.- How to Model and Verify Concurrent Algorithms for Distributed CSPs.- The Phase Transition in Distributed Constraint Satisfaction Problems: First Results.- Cooperating Constraint Solvers.- An Empirical Study of Probabilistic Arc Consistency as a Variable Ordering Heuristic.- On Dual Encodings for Non-binary Constraint Satisfaction Problems.- Algebraic Simplification Techniques for Propositional Satisfiability.- An Original Constraint Based Approach for Solving over Constrained Problems.- An Efficient Approximate Algorithm for Winner Determination in Combinatorial Auctions.