A process model is described for exchanging information in the building industry. In this model participants send and receive messages. On receipt of a message an activity is executed if all required information is available. Otherwise a message will be sent to another participant to obtain the missing information. After execution of an activity a reply is sent with the desired data. In a building project an agreement is defined with all activities that will be executed by each of the participants. An executable implementation of the process model is built in ExSpcct. In ExSpect the message exchange process can be simulated and analyzed for a specific building project.