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most efficient if the WebStore system exchanged information with existing
PVF systems rather than capture and store redundant information. This
analysis concluded that the WebStore should exchange information with
the Purchasing Fulfillment System (a system for tracking orders [see
Chapter 3 ]) and the Customer Tracking System (a system for managing
customer information). These two existing systems will be “sources”
(providers) and “sinks” (receivers) of information for the WebStore system.
When a customer opens an account, his or her information will be passed
from the WebStore system to the Customer Tracking System. When an
order is placed, information will be stored in the Purchasing Fulfillment
System. When a customer requests status information on a prior order,
information will be retrieved from the Purchase Fulfillment System.

Finally, Jim found that the system would need to access two additional
data sources. First, in order to produce an online product catalog, the
system would need to access the inventory database. Second, to store the
items a customer wanted to purchase in the WebStore’s shopping cart, a
temporary database would need to be created. Once a transaction is
completed, the shopping cart data can be deleted. With this information,
Jim was able to develop the level-0 DFD for the WebStore system, which is
shown in Figure 7-22 . He then felt that he had a good understanding of
how information would flow through the WebStore, of how a customer
would interact with the system, and of how the WebStore would share
information with existing PVF systems. Each of these high-level processes
would eventually need to be further decomposed before system design
could proceed. Yet, before doing that, he wanted to get a clear picture of
exactly what data were needed throughout the entire system. We will
discover the outcomes of this analysis activity—conceptual data modeling
—in Chapter 8 .

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Figure 7-22
Level-0 DFD for the WebStore

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