In which document do file specifications belong?

Question

In which document would a file specification belong? Perhaps this file is used as an input to a third-party system. Would it belong in its own document? Or would it be better to put it in the functional or design spec? Or somewhere else?

When I say file specification, I mean a description of what format the file is (CSV, fixed width, etc), columns, data types, etc.

Also, where should you document how the file is generated? i.e. business rules/algorithms which are used to generate the file.

Answer 1

I always document file formats and layouts in the design spec. Unless it is a simple file I document the layout in an Excel document embedded in the design spec.

Regarding your second question, the rule of thumb is the functional spec documents the "what" and the technical/design spec documents the "how". Business rules, triggering events, and algoritms should be documented in the functional spec. How your program implements those rules is documented in the technical design spec.