This figure demonstrates the example that is described in this section. This figure details the information flow inside an Interaction. This figure describes 5-steps involved in completing the client's Purchase Order. The first step involves the client invoking a takeOrder Reaction using session.call method. The client provides the Process context which has an Interaction ID, IID='user1' and a Process Activation ID, AID='AID_105_user1'. The takeOrder Reaction is fired inside a takeOrder Process. This step involves the following 3-sub steps: 2a. request a service from 'checkINV' Process (Reaction.call) 2b. request a service from 'checkCRED' Process (Reaction call) 2c. register a reaction, procPO (Reaction.registerReaction) In this example, the Reaction.call does not provide any IID or Process- AID. The AC4J infrastructure generates these for the call and uses them to start the checkINV and checkCRED processes. checkINV and checkCRED Processes return the processed information back to the callee Process, takeOrder. This is step number 3. Once the Data Tokens from checkINV and checkCRED are available from the respective Processes, the procPO Reaction gets fired. This Reaction is fired inside the takeOrder Process and executes the business logic. It finally returns the value to the client (through AC4J Databus--not shown). The fifth and final step involves the client 'pulling' the results from the AC4J Databus using the 'session.receiveReactionResponse. The client uses the same Interaction and Process Activation IDs that it used when it made the first request.