V FAQ : Basic Versioning Features : Why do we need DAV:precursor-set?
Clemm, Geoff [gclemm@rational.com] wrote in the deltaV mailing list: A workspace is only allowed to have one VCR for a given version history, to ensure that baselining and merging is unambiguous (baselining and merging in a workspace is based on finding the version history that corresponds to the version being merged), so if you want to create a “variant” of a resource in the same workspace, this requires two different version histories. In order to track the relationship between these two variants (i.e. when the diverged, and from what common version), the DAV:precursor-set property was introduced. It was then decided by the working group that this “history of a COPY” was something of general utility (using arguments similar to those that Rick posted), and since it provides utility with minimal server implementation cost, it was made part of the base protocol.
