| 1. Introduction With the development of network and distributed-database, the workflow, a new technique, came into being and is developing rapidly. The workflow technique separates the process logic from the application logic; manages the production process, business process or all processes integratedly; organizes people, information and application tools effectively; supports enterprises to realize DSS and the control of management and production. It can increase the reuse rate of software, consequently full play to max efficiency of the system. The theme of this paper roots in the System of Cooperated Design Management for MMI PLANNING&ENGINEERING INSTITUTE IX of the machinery ministry of China.The paper will discuss some topics about workflow as follows: Section 2 describes a kind of workflow system - J2EE-Based Distributed Multi-Engine Workflow System in detail; Section 3 discusses the mainframe of Domain Engine- the core part of DMEWf-System. Setion 4 gives a set of semantic specification of expression and its implementation in Java. Section 5 is about a kind of expanded transaction model (Multi-Level Saga Transaction model, briefly named MLST-Model). Section 6 is a conclusion.2. J2EE-Based Distributed Multi-Engine Workflow SystemFor the sake of the demand for distributed management of current business enterprises, this paper puts forward a system framework of workflow, namely J2EE-Based Distributed Multi-Engine Workflow System (it is called DMEWf-System for short). This framework depends on the Workflow Reference Model that is specified by Workflow Management Coalition. This system model is composed of Process Model, Organization Model and Resource Model. The Process Model depicts the process by the process defination graph, which is composed of some points and some directed edges. The point can be a simple point or a compound point. Directed edge has some information for selecting a path. Organization Model is composed of dynamic oraganization, static oraganization, role, right and user, and it has higher flexibility. This kind of organization model is able to describe the enterprises very well. In the Resource Model, the enterprises resource is splited into eight independent spaces by three axes: share, re-usability and dynamic. The whole system is made up of ControlCenter, Domain Engine, Organization Manger, Resource Manger, Worklist Manger and Audit Tool. These EJB components are distributed to diffent computers, and the workflow engines execute distributedly. The DMEWf-System has follow advantages: stronger process-describing ability, easy to use, flexible, extensible, good flexibility for application development, good transplantability and so on.3. The Mainframe of Domain EngineOn the basis of DMEWf system, the article illuminates the design of the Domain Engine of the system in detail. Because the DMEWf-System is a distributed multi-engine workflow system, its Domain Engine must implements some peculiar functions, e.g. the communication between two or more engines. So the functions of the Domain Engine are implemented by designing some components. These components include the self of Domain Engine, Service Manager, a lot of Repositories and Process Runner. All of the repositories are extended from the Class of AbstractRepository and implement the Interface of WorkflowService. The Process Runner is in charge of the running of a process instance, and the Domain Engine manages the creation of all kinds of instances, for example process instances, activity instances, workitem instances and so on. Moreover, it takes charge of the communication with other parts. The Service Manager controls all of the repositories. The Repositories are used to storage all kinds of Entities.4. Semantic Specification of ExpressionThis work defines semantic specification of expression that is necessary in workflow system, and builds a constructor for the abstract semantic tree of the expression and the Evaluator to caculate its value. This semantic specification of expression not only...
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