Systems Requirements Presentation

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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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