The Workflow Service

In our B2B application, the incoming document passes through a series of layers, each of which will perform some task on the document. The tasks performed by the document layers are somewhat generic actions such as document logging and XML validation. Such tasks are commonly applied to the document regardless of the content of the document and business logic that may be involved in processing the document. However, at some point, the document has to go through a number of business components that actually process the document. Unlike the tasks performed by the document layers, the business logic involved in the business components can be quite complex and dynamic. Compared with order of the document layers, which can be generically applied to the document, the order of the components and type of components participating in processing the document can be unique and highly dependent on the content of the document itself. For example, a purchase order from a trading partner may result in a completely different set of business components due to the relationship with the trading partner, the products in the purchase order, sales promotions, etc. In this chapter, we will look at a workflow service, which provides the architecture for coordinating the business components involved in document processing.