Study Of Directory Service In Migrating Workflow System

Migrating workflow is a kind of new technology that applies mobile computing to workflow management. It is especially suitable for the distributed concurrent process management in which huge data needs to be transmitted and many remote services need to be invoked frequently. The framework of migrating workflow management system is composed of three key elements, which are migrating workflow management engine, migrating instance(MI)and workplace. The migrating workflow management engine is in charge of the definition of workflow processes, generation of MI and coordination of multiple-ML A workplace consists of an anchorage server and several working-machine networks. The anchorage server is the place for MI' s execution, and correspondingly the working-machines provide workflow services for ML The MI, built on mobile agent technology, is the execution agent of tasks.In migrating workflow, the effective execution of the MI is mainly guaranteed by its itinerary graph. There are two kinds of itinerary graph, which are static itinerary graph and dynamic itinerary graph. Static itinerary graph is created when the migrating workflow is initialized and has a weak adaptability. Dynamic itinerary graph can be adjusted during the execution of migrating workflow. Therefore, it has a strong adaptability to the changes of workplaces and services. The generation of itinerary graph requires the information about the state of workplaces and services they provide. Therefore, a mechanism is needed to manage the information in migrating workflow and provide a method to access them effectively.Directory service is an effective information management measure developed in recent years. Based on the research in traditional directory service and LDAP protocol, the directory service in migrating workflow is studied in this paper. It needs to have characteristics as follows, 1) Hybrid directory service structure. Directory information requires being stored distributedly, which not only balances the burden of the engine and workplaces, but also prevents faults of a workplace from terminating the execution of migrating workflow. At the same time, it should provide a centralized measure to manage some global information and provide quick response to the query for the global information. 2) Dynamic adaptability. Migrating workflow system is a distributed system. Workplaces and services provided may change dynamically. The directory service is required to respond to these changes instantly. 3) Concurrency. In migrating workflow, it is needed that the directory service should provide quick response to multiple MIs' query. 4) Reliability. When the directory information is damaged, it should be able to recover instantly.According to the special requirements for directory service in migrating workflow system, a hybrid directory service module and architecture is proposed in this paper. The directory service component is also designed and implemented in detail. The experiment proves that it not only supports the generation of static itinerary graph, but also supports the dynamic modification of itinerary graph based on neighbor recommendation and the navigation of service. Therefore, the adaptability of itinerary graph is improved greatly.Since migrating workflow is a new research direction, there are still many issues to study on its directory service. The future work is to study the cooperative directory service model and the implementation method in migrating workflow to support the cooperative recommendation of workplaces and optimize the itinerary of migrating instance.