Proposes a computation model for cooperative agents. In this model, we introduce a field as an abstraction of a group of agents. Each agent can communicate to other agents in the same group through a field. The field also enables one to specify the action of the group, i.e. it is used for a knowledge base to keep the rules and data shared by the agents in the group. Based on this model, a programming language which is based on Prolog was designed, and a prototype processing system was built on a network-connected distributed multi-workstation system. We also present example programs written in this language to demonstrate the effectiveness of the model. >