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Arrgh, I wish to delete this, but do not know how. I cannot think of any So i will make it into a question. Georges' nice answer as good as is a presheaf that of Georges. I was trying to think violates the existence axiom s2 on every nbhd of a complementary one point. Is there an example that violated violates the uniqueness axiom s1 on every neighborhood nbhd of some point. Help, Georges?