An important component of each market is a set of current market sessions in which the actual agent interactions occur. Agents participating in a market may do so as either session initiators, or as clients, or both. Each session is initiated by a single agent for a particular purpose, and in general multiple agents may join an existing session as clients. The session is the vehicle through which market services are delivered dynamically to participating agents. It s erves as an encapsulation for a transaction in the market, as well as a persistent repository for the current state of the transaction.
Agents can play two different roles with respect to any given session.
The agent who initiates a session is known as t he session initiator, while other participating agents are known as session clients. A session can be initiated either for the purpose of buying or selling, depending on the type of market. In the above example of building a house, the initiating agent wa s the buyer or customer, and the other participants would be sellers or suppliers, whether they were supplying materials, labor, advice, credit, or other services. A session could also be initiated to sell items or services at auction. Figure 6 shows the structure of a session.