  A widely adopted approach to solving constraint satisfaction problems
combines systematic tree search with constraint propagation for pruning the
search space. Constraint propagation is performed by propagators implementing a
certain notion of consistency. Bounds consistency is the method of choice for
building propagators for arithmetic constraints and several global constraints
in the finite integer domain. However, there has been some confusion in the
definition of bounds consistency. In this paper we clarify the differences and
similarities among the three commonly used notions of bounds consistency.
