Abstract: The identification of parent child and ancestor descendant relationships among elements plays a crucial role in XML querying One popular method is to code an XML document structure by traversing orders of its elements Its main problem is that only determining ancestor descendant relationships can be captured but fail to predict parent child relationships Some deployments of the method lack the ability to support document update In this paper, a new coding scheme is proposed to identify the ancestor descendant relationship and/or the parent child relationship in constant time bounding It also supports XML document update