refinement step造句

Demands for spatial index directly come from spatial methods . in spatial database , spatial methods are implemented in two steps : first is filter step , in which spatial object ' s number is reduced through spatial index . second is refinement step , in which spatial objects resulted from filter step are subjected to exacted computation
空间索引的直接需求来自于大量空间对象上的空间运算，本文认为在空间数据库中空间运算应该分两步进行：第一步是筛选步骤，通过空间索引缩小进行比较的空间对象的个数；第二步为细化步骤，对从第一步中筛选出的空间对象进行精确的空间运算操作。
It's difficult to find refinement step in a sentence. 用refinement step造句挺难的