关键词: 物料清单, 遍历方法, 嵌套检查, 多层次通用件

Abstract: With the recursive traversal，non-recursion traversal and level traversal methods of BOM（Bill Of Material） and its wide
use of multi-level generic pieces and complex structure，this paper proposed an improved algorithm checking the overlaped nest and the legitimacy，which integrated the basic theory of DAG（Directed Acyclic Graph） chart and the practical net structure of BOM.This paper used the idea of top-down and layers decomposition，designed different signs and iteration to determine the current operation target，maked full use of the operation features in relational database，freed from memory constraints，the algorithm has a higher efficiency in implementation.

Key words: Bill Of Material（BOM）, traversal method, overlaped nesting check, multi-level generic pieces