Ilf

Internal Logical File (ILF) is a term used in Function Point Analysis (FPA). An ILF is a user-identifiable, logically related collection of data that is maintained by the application being measured and used by its functional processes. In practice, an ILF represents a data store within the system boundary that is controlled by the application and persists between transactions; it is distinguished from an External Interface File (EIF), which is maintained by another application and only used by the measuring application.

Counting ILFs is part of determining unadjusted function points. The size and complexity of an ILF are assessed by two factors: the number of Data Element Types (DETs) contained in the file and the number of Record Element Types (RETs) that describe the file structure. Based on these counts, the ILF is classified into a complexity level (low, average, or high), and a corresponding function point weight is assigned according to the counting method in use (for example IFPUG or similar standards).

Examples include a customer master file, an employee directory, or an order header file that the application creates, stores, and updates as part of its operation. If the data store is maintained by another system, it would be counted as an External Interface File (EIF) instead of an ILF.

ILFs are used alongside other function types to measure software size and to compare productivity and effort across projects. They emphasize the logical data maintained by the application rather than its physical storage.