Some documentation I found suggests that a GenBank GI number will change each time the sequence changes - even if only one base is affected. The Accession number, on the other hand, remains the same.
However, the accession number is usually qualified with a version number suffix, e.g. "GL000191.1". As far as I know, this version number also increments each time the sequence changes.
Does this mean that the relationship between GI number and the Accession.Version pair is one-to-one, and so either would be equally suitable as a unique identifier for a sequence?