"Along the Cardassian border" simply means where Federation space meets Cardassian space. If I said "I went to Fort Bliss. It's on the Mexican Border," I'd be referring to a place in the US. A Mexican could say "My Aunt lives in Juarez, on the US border." If Boone lives on the Cardassian side of the DMZ, that would mean he lives in the DMZ, on the Cardassian side, which by implication means there is also a Federation side. In real life, DM Zone and Neutral Zone seem to be part of each other. Neutral Zone would seem to imply "neutral ground" where two belligerents can be allowed "in the same space." When thinking of real life Demilitarized zones, I immediately think of Korea. The DMZ there is a true "No man's land," No one lives inside of it. It's heavily fortified on either side and mined in the middle. It's 4km wide and extends the entire border of North and South Korea. No military may step inside. Part of the Han River Estuary is called the "neutral zone" and its an area where no civilian ships may enter. Vietnam had a Demilitarized Zone very similar to Korea. It was about twice as wide, heavily fortified on each side, and no military could enter.