From UFStarfleet Wiki
From Wikipedia (Search: Star Trek Canon)
- “The Star Trek canon is usually defined as comprising the television series, Star Trek, Star Trek: The Next Generation, Star Trek: Deep Space Nine, Star trek: Voyager, Star Trek: Enterprise and the motion pictures and excluding everything else. However, the official Star Trek website acknowledges that this definition is not set in stone, but that the notion of what constitutes canon is fluid, open to interpretation and debate.”
Since we have non-canon creatures, ships, Marines and a couple of Data’s relations, the United Federation Starfleet is considered to be part of that fluid aspect of Star Trek. Forever changing, forever moving forward.