Inter-file branching a practical method for representing variants

Abstract

Contemporary software configuration management (SCM) systems identify variants in the same namespace that identifies revisions. The variants -- the alternate implementations of a configuration item that must exist in parallel -- and revisions -- the iterative refinements that each variant takes on over time -- form a two dimensional version tree for a configuration item. So typically a configuration item will have two names: one that names the item and another that names the version. This paper presents an alternate approach where the identification of a variant is moved into the name of the configuration item, leaving the version namespace only a linear set of revisions. Because this method has been realized in a working system where the configuration items are software source files, it is called Inter-File Branching. Branching is the act of creating variants, files are the configuration items, and inter-file reflects that fact that variants are separate files.