19.3. Implementing Workflow Association and Initiation
For a workflow to be useable on a SharePoint site, it must first be associated with a list, a library, or a particular content type. As a Web designer, you have to make this choice based on your requirements. After the workflow is associated with a list or a library, an instance of it can be started by firing it manually or setting it to automatically start whenever an item is created or changed.
NOTE
Only a single instance of a workflow can be run on a list item at one time. This means that while an instance of a workflow is running on an item, you can't start another instance of the same workflow on the same item. You can, however, start an instance of another workflow on the item. It's recommended that you don't run more than 15 workflow instances on the same item at one time.
You can associate a workflow with the following SharePoint assets:
Associate with Lists: When you associate a workflow with a list, instances of the workflow can be started for the items in the list. The item on which the workflow is running is called the Current Item in the workflow context.
Associate with Libraries: After the workflow is associated with a library, its instances can be run on the document, pictures, etc., that belong to the library.
Associate with Content Type: By allowing you to associate a workflow with a particular content type, SharePoint lets you use a single workflow across multiple lists and libraries that use that content type.
NOTE
Workflows created with SharePoint Designer can't be associated with SharePoint content types.
Workflows created for SharePoint lists and libraries can be started (or initialized) in the following ways:
Automatically when an item is created: When creating a workflow, you can specify that it should start whenever an item is created in a list or a library.
Automatically when an item is updated: This option triggers an instance of the workflow on an item when the item is changed.
Manually: You can also configure a workflow to be manually started on an item in the list or library. When users start the workflow manually, they're taken to a workflow initiation Web page. The initiation Web page consists of a user interface that can be used to start the workflow. Optionally, designers can also request user input at the start of the workflow by customizing the initiation page to include fields for user input.
SharePoint Designer allows Web designers to choose whether the workflows should be started manually or automatically. You can also design a custom initiation Web page with a form that can be used to request user input. The user input can then be stored in variables that form the workflow data and are used for performing the business logic the workflow is designed for.