External Interface Files

External Interface Files (EIF) - a user identifiable group of logically related data that is used for reference purposes only. The data resides entirely outside the application boundary and is maintained by another applications external inputs. The external interface file is an internal logical file for another application. An application may count a file as either a EIF or ILF not both. An external interface file has the inherent meaning it is externally maintained (probably by some other application), an interface has to be developed to get the data and it is stored in a file.

Each EIF included in a function point count must have at least one external output or external interface file against it. At least one transaction, external input, external output or external inquiry should include the EIF as a FTR.

Every application, which references the EIF, needs to include it in their FP Count. Some organizations have a pull theory and others have a push theory of data. The pull theory is an external application "reaching into" another applications and retrieving data. Those organizations which have push theory require applications to create interfaces (EO or EQ) which other applications read.