This book constitutes the thoroughly refereed post-proceedings of the Joint ERCIM/Compulog-Net Workshop on New Trends in Constraints held in Paphos, Cyprus, Greece in October 1999. The book is divided in topical sections on constraint propagation and manipulation, constraint programming, and rule-based constraint programming.

Invited Contributions and Surveys.- Interval Constraints: Results and Perspectives.- A Constraint-Based Language for Virtual Agents.- Constraint (Logic) Programming: A Survey on Research and Applications.- OPL Script: Composing and Controlling Models.- Constraint Propagation and Manipulation.- Some Remarks on Boolean Constraint Propagation.- Abstracting Soft Constraints.- Decomposable Constraints.- Generating Propagation Rules for Finite Domains: A Mixed Approach.- Ways of Maintaining Arc Consistency in Search Using the Cartesian Representation.- Constraint Programming.- Combining Constraint Logic Programming Techniques for Solving Linear Problems.- Quantitative Observables and Averages in Probabilistic Constraint Programming.- Dynamic Constraint Models for Planning and Scheduling Problems.- A Finite Domain CLP Solver on Top of Mercury.- Rule-Based Constraint Programming.- Rule Based Programming with Constraints and Strategies.- Proving Termination of Constraint Solver Programs.- Projection in Adaptive Constraint Handling.