1)line progenitor,系统祖先2)ancestral lineage,祖先世系3)ancestral series,祖先系列4)umbilic(al) ancestor,母系祖先5)A direct ancestor.,祖先直系的祖辈6)ancestor/descendent relationship,祖先/后代关系
用法例句
Nowadays query for XML document is a hotspot of research,in which twig pattern matching is an important direction of research,but most algorithms based on the method can only process query containing ancestor/descendent relationship.