Beginning Web Development, Silverlight, and ASP.NET AJAX

CHAPTER 9
.NET 3.0: Windows Workflow
Foundation
Workflow is what happens when an item is moved through various stages or people
through a fixed business process. This process contains a number of steps or activities
that can be acted on by machines, people, or a combination of both, and can involve various
rules. For example, when you first join a new company, a set of business processes
gets invoked. You need to be added to payroll, you need an office to be assigned, equipment
and furniture need to be set up, and so on. Behind the scenes, a business process
kicks in for the new hire. Or, when a company sells something, it typically begins with
receipt of a purchase order. The purchase order has to be entered into the business system.
This sets up a requisition for the product from stock. If not enough of the product is
available, more needs to be ordered. When enough of the product is available, it is moved
to shipping. Shipping boxes them up and sends them to the customer. Billing then generates
an invoice to send to the customer. Billing also tracks payment, and if the customer
pays, the order is flagged as such. If they don’t pay by the time of the terms of the invoice,
a new process for collections is kicked in.
Throughout this entire scenario, an “item,” the purchase requisition, flows throughout
the system. The item morphs and changes throughout, but as you can see from this
example, it changes into what makes sense for the current stage in the process. The entire
scenario is termed a workflow, and each of the actionable elements in it (entering the
purchase order, building the order, etc.) is termed an activity.
A workflow isn’t always linear. In fact, it is rarely linear. In the preceding scenario, the
workflow could have gone in different directions based on different scenarios. For example,
if the company has enough stock of whatever was ordered, the next step is to go to
shipping and billing. If it doesn’t, the next step is to order new product and wait for the
order to be fulfilled before it can go to shipping and billing. In this case, it is likely that a
customer service workflow, informing the customer of the delay, would also kick in. This
is what is called branching in workflow terminology.
There are a number of different types of possible workflows. The preceding example
is what is known as a sequential workflow, where the item flows from a known beginning
point (receipt of the order) to a known endpoint (shipping, billing, and collecting).
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