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Analysis and Design
DFD Example - General model of publisher's present ordering system
Following are the set of DFDs drawn for the General model of publisher's present
First Level DFD
Second Level DFD - Showing Order Verification & credit check
Third Level DFD - Elaborating an order processing & shipping
Fourth level DFD : Completed DFD, Showing Account Receivable Routine.
From the level one it shows the publisher's present ordering system. Let's
expand process order to elaborate on the logical functions of the system. First,
incoming orders are checked for correct book titles, author's names, and other
information and then batched into other book orders from the same bookstore to
determine how may copies can be shipped through the ware house. Also, the credit
status of each book stores is checked before shipment is authorized. Each shipment
has a shipping notice detailing the kind and numbers of booked shipped. This is
compared to the original order received (by mail or phone) to ascertain its accuracy.
The details of the order are normally available in a special file or data store,
called "Bookstore Orders". It is shown in the second level DFD diagram.
Following the order verification and credit check, a clerk batches the order
by assembling all the book titles ordered by the bookstore. The batched order
is sent to the warehouse with authorization to pack and ship the books to the
customer. It is shown in the third level DFD diagram.
Further expansion of the DFD focuses on the steps in billing the bookstore
shown in the fourth level DFD, additional functions related to accounts receivable.
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