Validation of a protocol for communication management in CSCW systems using a coloured-Petri net modelization

The communication protocol called Chameleon allows users to work over a collaborative platform. This protocol is based on revolutions between active sites of a token which contains the shared objects modified. Indeed, if one site is not active for a certain delay, it becomes inactive, and only token copies are transmitted to this site. To become active again, an inactive site has to send a signal to its tutor. In this protocol, one site can update the shared memory only if it is the owner of the active token. So, there are concurrent treatments (sites becoming active and inactive, updating, active token transmissions, ...) and messages (active token, token copies, activity requests) between the sites. In order to verify our protocol, we modelized it using a coloured Petri Net and made a qualitative study of this protocol verifying the properties of the obtained model. Indeed, we have verified that the state of each site is never lost, the active token also, and the fact that all the signals are treated. Furthermore, we verified that no more than one site can enter in critical section. The exclusive property has been verified. Nevertheless, this study does neither consider the delays nor the frequency of updating using the Chameleon. Our future work will consist on a quantitative study using stochastic Petri Nets.