With a basic grounding in WF fundamentals, it is now possible to understand workflow in the context of Windows SharePoint Services. Since MOSS builds on WSS, it gets all of its workflow capabilities through WSS. Therefore, to understand workflow in MOSS, you also need to examine how WSS hosts the WF runtime.
Recall that Windows Workflow Foundation is not itself an application but merely provides a framework for workflow development. In order to execute a workflow, the WF runtime engine must be hosted within an execution environment. The WF runtime then interacts with that environment through a prescribed set of interfaces in order to create the required conditions for performing each workflow activity. It is important, therefore, to keep in mind that WSS hosts the WF runtime differently than most other applications. This fact becomes immediately apparent as soon as you start to peek inside the WSS host implementation.
The first thing to consider is the high-level design of the WSS workflow hosting environment. Given the nature of the SharePoint environment, two assumptions are immutable. Workflows will be centered around content, and workflows will involve interactions with people. The following two sections explore these design constraints in greater detail.
The content-centric nature of SharePoint workflow is readily apparent, but it also affects the design of the ...