Study On Trust-Based Coalition Formation In Migrating Workflow

Migrating workflow is a new direction in the area of workflow management research these years. A novel workflow framework based on mobile computing paradigm, which includes the workflow engine, the workplace and the migrating instance, is proposed in our former research. A migrating workflow engine creates migrating instances according to business processes. When created, the migrating instance migrates from one workplace to another, using run-time service and workflow service to execute the business process. Due to advantages such as its support to business process execution with an offline workflow engine as well as reducing network load and network latency, it has drawn considerable attention of people in both the laboratory and the business.Though overcoming disadvantages that are common in distributed system and traditional workflow, migrating workflow is far from guaranteeing the security and efficiency of business process execution. To solve these problems, a trust model in migrating workflow is proposed, a trust-based migrating workflow coalition formation method is given as well. A coalition is defined as a group of agents with common goals, in which tasks are assigned and information is shared. Coalition formation is the procedure to establish relationship such as task assignment and result sharing according to the coalition's common goals and rules, through which the workflow engine can select a set of optimal workplaces to support business processes. Trust is usually adopted as the strategy to form a coalition.Trust is defined as the attitude an agent has with respect to the dependability/ capabilities of some other agent (maybe itself) or with respect to the turn of events and is the way for an agent to choose partners based on its cooperation. Trust can be categorized by confidence and reputation, while confidence is derived from analyzing the result of previous interactions with that agent, reputation is acquired from the experiences of other agents in the community through gossip or by analyzing signals sent by an agent. To meet the requirement for business acquaintance recommendation, confidence of a workflow engine in a workplace is divided into two parts, recommendation confidence and capability confidence. Reputation of a workflow engine in a workplace as well as trust between workplaces are also discussed.Since trust is adopted as the coalition formation strategy in migrating workflow, the coalition manager can form a workflow coalition according to the contract net protocol, as well as organize a workflow domain according to the coalition structure generation method. A workflow coalition is a long-term coalition, which maintains static relationships among coalition members, enhances system stability, benefits coalition members as well as lowers complexity of computation and communication. A workflow domain is a short-term coalition, a team of agents that cooperate for a single goal and is viewed as dynamic relationships among coalition members. When generated, the optimal workplace coalition, which is also known as the workflow domain, will serve as a group of workplaces with the maximum trust values that can guarantee execution of a business process.As a key question in migrating workflow research, trust-based coalition formation mechanism has been implemented and simulated on our mobile computing cooperative product commerce platform. The results have proved that our trust model and coalition formation mechanism can guarantee the security and efficiency of business process execution. Update of cooperation evaluation, trust calculation and coalition formation procedure can be done in polynomial time, which can ensure workflow deployment in a larger scale as well as with high efficiency.