To start with, however, we
need a bit more background about what we??™re actually trying to achieve.
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C H A P T E R 1 8
What Is an Order Pipeline?
Any commercial transaction, whether in a shop on the street, over the Internet, or anywhere
else, has several related tasks that must be carried out before it can be considered complete.
For example, we can??™t simply remove an item of clothing from a fashion boutique (without
paying) and say that we??™ve bought it??”remuneration is an integral part of any purchase. In
addition, a transaction completes successfully only if each of the tasks carried out completes
successfully. If a customer??™s credit card is rejected, for example, then no funds can be charged
to it, so a purchase can??™t be made.
The sequence of tasks in a transaction is often thought of in terms of a pipeline. In this
analogy, orders start at one end of the pipe and come out of the other end when they are
completed. Along the way, they must pass through several pipeline sections, each of which
is responsible for a particular task or a related group of tasks. If any pipeline section fails to
complete, then the order ???gets ???stuck??? and might require outside interaction before it can
move further along the pipeline, or it might be canceled completely.
For example, the simple pipeline shown in Figure 18-1 applies to transactions in a brickand-
mortar store.
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