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Transactional Functions (External Inputs, External Outputs, and External Inquiries)

Transactional Function Definitions

  • IFPUG defines an external input (EI) as an elementary process of the application that processes data or control information that enters from outside the boundary of the application. Processed data maintains one or more ILFs; processed control information may or may not maintain an ILF. The primary intent of an EI is to maintain one or more ILFs or to alter the behavior of the application through its processing logic.

  • IFPUG defines an external output (EO) as an elementary process of the application that generates data or control information that exits the boundary of the application. The primary intent of an external output is to present information to a user through processing logic other than, or in addition to, the retrieval of data or control information. The processing logic must contain at least one mathematical formula or calculation, create derived data, maintain one or more ILFs, or alter the behavior of the system.

  • IFPUG defines an external inquiry (EQ) as an elementary process of the application that results in retrieval of data or control information that is sent outside the application boundary. The primary intent is to present information to a user through the retrieval of data or control information from an ILF or EIF. The processing logic contains no mathematical formulas or calculations and creates no derived data. No ILF is maintained during processing, and the behavior of the application is not altered.

Step 4 in the function point counting process is to identify the transactional functions. The clerk updates Location directory data as an external input (EI). The Location listing, which includes totals, is generated as an external output (EO). Building security personnel request the retrieval and display, an external inquiry (EQ), of information maintained in the Location directory ILF, as well as employee data from an EIF, currently maintained in the Personnel application. An EQ can retrieve data from one or more ILFs or EIFs.

These are examples of only the functional components within an application. If you can understand these concepts, you are well on your way to counting function points. Function point analysis provides a well-defined, internationally accepted process for sizing software. The timing of the counts varies depending on the particular status of an application. Typically, less information is available early in the definition or requirements phase of a project. Significantly more information is available as an application is developed and delivered.

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