在Abel范畴中定义子对象的和,并利用拉回与推出给出子对象交与和的等价定义,证明子对象的交与和满足结合律,以及Abel范畴上的模律与蝴蝶引理.
Define the sum of subobjects in abelian categories,Introduce the altermative definitions of the intersection and the sum of subobjects by using the technology of pullbacks and pushouts.And then prove the operations of intersections and sums to satisfy associative law,and the modular law and butterfly lemma in abelian categories are given.