2009年1月26日 星期一

Real Analysis - Orderings

A Partial Ordering is a relation ≤ such that
  1. a ≤ a (refective property)
  2. a ≤ b and b ≤ c ⇒ a ≤ c (transitive property)

We call a partial ordering antisymmetric if

  • a ≤ b and b ≤ a ⇒ a = b

A partial ordering ≤ is called a total ordering if

  • Either a ≤ b or b ≤ a
  • A total ordering ≤ is called a linear ordering if it is antisymmetric.

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