The Study Of Service Composition Based On Ontology In Migrating Workflow System

Migrating workflow becomes a new research trending in the area of workflow these years, and by implementing with mobile agent technology, it supports for decentralization and loose coupling characteristics of the workflow management. Migrating workflow includes the migrating workflow engine, the workplace and the migrating instance, is a new model of the workflow management. When created, the migrating instance migrates from one workplace to another, using service to execute the business process. A migrating workflow engine creates migrating instances according to business processes. 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.Migrating instance can move continuously among the work positions and use their services to complete tasks, when the current work position cannot meet its requirement, it will carry the goal and current result to move to another which meets the requirement to continue executing, the workflow services of work position are limited and do not always meet the goal, then there will need to compose existing services to meet the task requirement.Service composition is to compose the workflow service of the workplace to generate the large-grained services which can meet the goal of the migrating instance. To ensure the migrating instance and work position can understand each other in the service semantic level; we introduce the definition of ontology. This paper proposes a migrating workflow model based on ontology, in this model, migrating workflow domain ontology describes all the participants in the workflow. the model gives the clear definition of instance, its goal, service and service evaluation, and also gives the definition of acquaintance of workplace, class of serve and service relationship, it gives the complete description of migrating workflow based on ontology. Then based on the model, we propose the framework of service composition in migrating workflow, and describe the process of service composition according the goal of migrating instance clearly, illustrate the method to get the set of class of service and class of service relationship net clearly, based on this, we give the method of service composition and deal with the service which composes to get the new service to achieve the reuse of services, this method can get the service composition which meets the goal of migrating instance dynamically. We also give the determination method of service instance, in which considers the quality of service and acquaintance relationship, this method ensures the quality and efficiency.According to the method this paper proposes, it is fulfilled on migrating workflow management system in mobile computing lab. Through the example simulation, it is illustrated that our method can get the service composition which meets the goal of migrating instance dynamically; this method ensures the quality and efficiency and improves the flexibility of workflow.