We propose constraints as the appropriate computational constructs for the design of agents with the task of selecting, merging and managing electronic information coming from such services as Internet access, digital libraries, E-mail, or on-line information repositories. Speci cally, w e i n troduce the framework of Constraint-Based Knowledge Brokers, which are concurrent agents that use so-called signed f e ature c onstraints to represent partially speci ed information and can exibly cooperate in the management of distributed knowledge. We illustrate our approach b y several examples, and we de ne application scenarios based on related technology such a s T elescript and work ow management systems.