1.The definition of Binary Relation.
A subset of The Cartesian product.
2.Some basic concepts：
Reflexive, Irreflexive, Symmetric , Asymmetric, Transitive, Negatively Tansitive ,Completeness.
3.What is P_model, the rational conditions of this model; What is ≧_model, the rational conditions of this model.
4.The proof of P_model and ≧_model are equivalent.
5.The definition of Choice Correspondence.
6.The two definitions of WARP.
7.Sen's Property alpha and Beta.The relationship between WARP and Sen' property Alpha and Beta.
8.The definition of Rationalized.
9.The proof of C can be rationalized iff C satisfies WARP（Sen's property Alpha——C is a Choice function.）*
