Partitioning is the process of examining a data flow diagram and determining how it should be divided into collections of manual procedures and collections of computer programs. Analyze each process to determine whether it should be a manual or automated procedure. Group automated procedures into a series of computer programs. A dashed line is often drawn around a process or group of processes that should be placed into a single computer program.
There are six reasons for partitioning data flow diagrams:
- Different user groups. Are the processes performed by several different user groups, often at different physical locations in the company? If so, they should be partitioned into different computer programs. An example is the need to process customer returns and customer payments in a department store. Both processes involve obtaining financial information that is used to adjust customer accounts (subtracting from the amount the customer owes), but they are performed by different people at different locations. Each group needs a different screen for recording the particulars of the transaction, either a credit screen or a payment screen.
- Timing. Examine the timing of the processes. If two processes execute at different times, they cannot be grouped into one program. Timing issues may also involve how much data is presented at one time on a Web page. If an ecommerce site has rather lengthy Web pages for ordering items or making an airline reservation, the Web pages may be partitioned into separate programs that format and present the data.
- Similar tasks. If two processes perform similar tasks, they may be grouped into one computer program.
- Efficiency. Several processes may be combined into one program for efficient processing. For example, if a series of reports needs to use the same large input files, producing them together may save considerable computer run time.
- Consistency of data. Processes may be combined into one program for consistency of data. For example, a credit card company may take a “snapshot” and produce a variety of reports at the same time just so figures are consistent.
- Security. Processes may be partitioned into different programs for security reasons. A dashed line may be placed around Web pages that are on a secure server to separate them from those Web pages on a server that is not secured. A Web page that is used for obtaining the user’s identification and password is usually partitioned from order entry or other business pages.