Function Points FAQs
Duplicate Counting of Front-end and Core System Functions
Due to the unique characteristics of the application boundary between separately-counted front-end and core systems, it is possible for duplication of functionality to occur. Should logical transactions therefore be double counted, replicating the core system transaction in the front-end?
In this example the Front End System (FES) user views the enquiry as a transaction in its own right and one that belongs to the FES application. The user has no knowledge that both the FES and Core applications are required to process the transaction. When the transaction is viewed as two parts, each part-of the transaction will reference the same files and data elements. This situation is shown in the following diagram.
There are two possible scenarios for transactions that pass between the front-end and host applications:
Both FES and Core systems must do work in order for the transaction to complete successfully.
The Core system may be unaware of a functional requirement to supply information; i.e. the FES application does all required work in order for the transaction to complete successfully. In other words, the FES has all the required functionality to directly read data from the Core system files and process the enquiry.
The question is whether logical transactions should be double counted because of the positioning of the application boundary.
GENERAL DISCUSSION AND RESOLUTION
As most applications are counted in isolation (i.e. not counted with all their interfacing applications at the same time), it is often difficult to establish that a transaction may be contributing only part of a logical transaction. The same logical transaction should be counted as separate transactions where both application project teams are required to expend work effort in order to deliver the complete transaction.
Where one application team does all the work to provide the data for the transaction, then the transaction should be counted as one logical transaction credited solely to that application.
The systems messages, which may be sent between the FES and Core system, requesting the information, and providing the data response, are not to be counted as additional EO's and EI's. This messaging is part of the technical solution to satisfy the user requirement to Enquire on Account Details. The double counting of the function by the FES and Core system has been accepted as a pragmatic solution resulting from the positioning of the application boundary. Counting of the system messages as well would result in unacceptable 'double counting'.