So, in First Contact, Admiral Hayes awakens Picard with the news from DS5 that "our colony on Ivor Prime was destroyed this morning".
(Note that this is a very different sort of scenario than what we saw with Jouret IV at the start of "The Best of Both Worlds" . . . in that case, the colony was destroyed but there was a significant delay in this being found out. But I digress . . . )
When Picard briefs his officers sometime later, he notes that the Borg will cross the Federation border in less than an hour.
So wait . . . what's the story with Ivor Prime, then? The Federation has a colony there but they consider it outside their border?
This is a bit odd. Either it's within someone else's border (could it be a Cardie DMZ world? Or within the territory of some species like the Sheliak but friendlier (i.e. they can't settle it but they let the Federation)?) or it's in non-aligned space that the Federation has planted a colony on but not claimed.
The whole bit about the border would be interesting in the latter case, because that would suggest declared borders without someone else around to make them meaningful. That doesn't make too much sense, really, unless the "border" is more of an informal term relating to the territory of the Federation core systems.
Note here that I'm against the "swiss cheese Federation" concept wherever possible, but Ivor Prime does seem to suggest some non-contiguous-ness.
The thought that Ivor Prime is related in some fashion to the Cardassian DMZ thing is interesting, except one would think a Borg attack, even if it was on a formerly Federation colony, would have given the Cardassians and Dominion some pause (or maybe it did, and that's why they didn't attack for a bit longer).
Anyway, I don't have an answer here . . . it's just an odd bit worth a few minutes pondering.