Workflows: Workflows in WSS 3.0 and MOSS 2007

Workflow Templates and Instances
In Windows SharePoint Services, workflows that are available on a site or list are referred to as workflow templates; a workflow that is actually running on a specific SharePoint item is called a workflow instance. So, on a given list, several instances of the same workflow template may be running at the same time, each on a different SharePoint item. More than one workflow can be running on a given SharePoint item at a time.
Points of User Interaction with Workflows
Let's look more closely at the various stages at which users can interact with workflows in Windows SharePoint Services and SharePoint Server.

A. Association
Association occurs when a site administrator makes the workflow template available on a specific document library, list, or content type. At this stage, the site administrator customizes the workflow for this specific document library, list, or content type by specifying the following parameter information:

• A unique name for the workflow
• How the workflow is applied to a given item: either automatically when the item is created or changed, or manually; and which roles, such as Administrator or Contributor, can start a workflow
• The Task list, in which the workflow can create tasks
• The History list in which the workflow can store history events, as defined by the workflow

In addition, the workflow developer can enable the site administration to further customize the workflow by setting parameter information specific to the particular workflow. The administrator may have to specify parameters, default values, and other information for the workflow as it applies to items on the list, library, or content type with which the administrator is associating it.
Associating a workflow actually occurs outside the workflow itself; no workflow instance is actually started during association. Rather, Windows SharePoint Services stores the association information in a special internal workflow association table. Then, when the workflow instance is actually started, Windows SharePoint Services uses the association data (and the initiation data, if any) to set the parameters of the new workflow instance.

B. Initiation
Whereas association deals with the workflow as it applies to a specific list, library, or content type, initiation deals with the workflow as it applies to a specific SharePoint item.
Initiation occurs when a user actually starts a workflow instance on a specific item. The user supplies information custom to that specific workflow on that item, if necessary, and then starts the workflow.
Workflow developers can use initiation to let users override or append the association parameters set by administrators, or specify additional parameters or information about the workflow as it applies to the given SharePoint item. Not all workflows need initiation. In fact, a workflow set to start automatically cannot have initiation parameters.
The Windows SharePoint Services workflow project for the Visual Studio 2008 Designer for Windows Workflow Foundation includes an activity that acts as the event handler when the workflow is initiated. This activity is the first activity in any Windows SharePoint Services workflow.

C. Modification
Modifications enable users to alter the parameters or flow of a workflow instance as it is running. As a developer, you may have points in your workflow at which you would like to enable users to alter the workflow while it is running on an item. For example, you might want to enable a user to assign a task to another person, or even add a specific task to the workflow. The options you present to users to change the workflow as it is running on an item are called modifications.
The Windows SharePoint Services workflow project for the Visual Studio 2008 Designer for Windows Workflow Foundation includes an activity to enable a workflow modification, as well as an activity that acts as an event handler when a workflow modification is enabled.

D. Tasks
Workflow activities that are performed by people are represented as tasks in Windows SharePoint Services workflows.
As workflow author, you can specify the task schema. For example, the task listing could include the following:

• Task title
• Name of person to whom the task is assigned
• Task status
• Task priority
• Task date due
• A link to the referenced item

The user can then edit the task as necessary. The workflow instance is notified of changes to workflow tasks and can choose to respond to them as specified in the workflow.
The Windows SharePoint Services workflow project for the Visual Studio 2008 Designer for Windows Workflow Foundation includes activities that create, delete, and update tasks, as well as activities that act as event handlers when tasks are created, updated, or deleted.