Relations and Their Basic Properties
Relations and Their Basic Properties
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关系及其基本属性
DOI:
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发表时间:
2004
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通讯作者:
Edmund Woronowicz
中科院分区:
文献类型:
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作者:
Edmund Woronowicz
We define here: mode Relation as a set of pairs, the domain, the codomain, and the field of relation; the empty and the identity relations, the composition of relations, the image and the inverse image of a set under a relation. Two predicates, = and ⊆, and three functions, ∪, ∩ and \ are redefined. Basic facts about the above mentioned notions are presented. The articles [2] and [1] provide the notation and terminology for this paper. Let I 1 be a set. We say that I 1 is relation-like if and only if: (Def. 1) If x ∈ I 1 , then there exist y, z such that x = y, z. Let us note that there exists a set which is relation-like and empty. A binary relation is a relation-like set. denote binary relations. We now state four propositions: (3) 1 If A ⊆ R, then A is relation-like. (4) {{ x, y } is relation-like. The scheme Rel Existence deals with sets A, B and a binary predicate P , and states that: There exists a binary relation R such that for all x, y holds x, y ∈ R iff x ∈ A and y ∈ B and P [x, y] for all values of the parameters. Let us consider P, R. Let us observe that P = R if and only if: (Def. 2) For all a, b holds a, b ∈ P iff a, b ∈ R. 1 The propositions (1) and (2) have been removed.