Characterization of certain choice functions
We characterize rationality of certain choice functions C by C(A) ∩ C(B) ⊇ C(A ∪ B) ⊆ C(A) ∪ C(B). We also characterize choice functions coming from preference relations which are partial orders and some other types of relations. Furthermore, we also characterize the admissible set of a binary relation by the fact it is invariant under certain changes in the relation.