A policy that relates attributes of an agent to a role is distributed to each agent on a network. A field connector generates an internal field in accordance with an instruction of a security manager. A ROLE manager uses attribute information from an attribute manager, and assigns each agent a ROLE in accordance with the attributes of each agent, and installs a ROLE method table and a ROLE execution part. When receiving a message from an external network, each agent searches for a corresponding ROLE by referring to the ROLE method table, and executes the ROLE. Thus, collaboration among agents is realized through a virtual communication channel by means of the exchange of a message.