Please note that while there have been a bunch of suggestions for 'burrows that don't let dwarfs in/path through', I've checked the forums pretty carefully, and this is not the same thing.
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Right now, burrows are essentially 'inclusive'. In other words, suppose you define a burrow around a mason's workshop and assign a dwarf to it. That dwarf will only take jobs within the burrow; however, any other idle dwarfs with masonry enabled will also work at that masonry workshop. The dwarfs allowed to take jobs in the burrow are the union of (the set of dwarfs assigned to the burrow) and (the set of dwarfs not assigned to the burrow).
What I'd like to see would be a way to toggle burrows between being 'inclusive' and 'exclusive'. An inclusive burrow would work just like burrows do now. An exclusive burrow would only allow jobs to be taken by dwarfs assigned to the burrow; dwarfs that were not assigned to the burrow would not take jobs from the burrow. So, if you made an inclusive burrow around a dining hall, all dwarfs could eat in the hall; dwarfs assigned to the burrow could only use that dining hall. If you made an exclusive burrow around a dining hall, only the dwarfs assigned to the burrow could use the hall.