ng Abstractions for Local Search Pascal Van Hentenryck1 and Laurent Michel2 1 Brown University, Box 1910, Providence, RI 02912 2 University of Connecticut, Storrs, CT 06269-3155 Abstract. Comet is an object-oriented language supporting a constraintbased architecture for local search. This paper presents a collection of abstractions, inspired by constraint-based schedulers, to simplify scheduling algorithms by local search in Comet. The main innovation is the comal model underlying the abstractions. Its core is a precedence graph which incrementally maintains a candidate schedule at every computation step. Organized around this precedence graph are differentiable objects, e.g., resources and objective functions, which support queries to define and evaluate local moves. The abstractions enable Comet programs to feature declarative components strikingly similar to those of constraint-based schedulers and search components expressed with highlevel modeling objects and control structures....