Study On An Embedded Light Weight Workflow Engine

Workflow engine is the core of a workflow management system. It explains workflow model definition, controls and maintenances how a workflow instance works. To implement an embedded lightweight workflow engine based on Web is the main purpose. Aiming at special business processes of power plants, the workflow engine is designed to be particular business logical dominated and flexible in given domain, but less general.Certain process structure can be viewed as a graph. Nodes in it indicate activities and lines denote direction control. To make roles and users who tackling tasks as a node in process graph directly can lead to define process activities easily. Based on process model definition described by relational structure, direction control logical realizes Sequence, XOR-Split and XOR-Join, And-Split and And-Join transition types. Message notification mechanism based on Web implements tasks assignment of certain and uncertain processes. Lock and unlock mechanism makes tasks that can be handled by nodes reasonably. Concurrency control of tasks solves the risk that more than one man may handle the same task at the same time under B/S pattern.Accommodating with the distributed component software design trend, Web Services can be adopted to encapsulate workflow engine so that some other systems can use process services provided by workflow engine as modules of themselves. Thus, the workflow engine can be embedded in other system.Relational structure is used to define data handled by workflow engine, so these data can be exchanged with other data in the same system straight and efficiently managed by DBMS. Workflow engine is restricted to handle special processes of power plants, thus it is powerful in this domain but lightweight and implemented easily. The core modules direction control and message notification mechanism with particular characteristics run well in AMS system. Encapsulated with Web Services, the workflow engine can be embedded in other systems, so that AMS can be upgraded and pushed to Internet easily.