Token Finding Strategies

Monitoring distributed computations provides a practical way of learning about and coming to understand a class of applications that are becoming increasingly common. The beneets of distribution arise from processes cooperating together to achieve a common goal. Coordination among the processes is a fundamental ingredient for the cooperation to occur both correctly and eeciently. One common form of coordination is token passing, where a token enables the process holding it to perform some action(s). In order to better understand this form of coordination it is useful to be able to monitor the process that holds the token, as the token moves from one process to another. Unless the token is being continuously monitored though the initial step is to nd the location of the token to enable subsequent monitoring of it. We describe a classiication scheme for token nding strategies. Token-nding algorithms make use of information about the environment and application to make the search more eecient. The information examine in detail is the interconnection of the logical processes. We describe the Pathhnder system which uses agents to implement token nding strategies. The exibility aaorded by agents allows them to make use of environmental information at run time.