Using a native XML DBMS to efficiently store and retrieve XML data has been well studied in recent years. Various native XML DBMSs were developed, and they support most of the features of XQuery. The core topics of these studies are indexing methods for XML. There are two major issues about the existing XML DBMSs: (1) Most existing native XML DBMSs use range based indexing methods, resulting in significant extra space; (2) related information in an XML document are isolated in storage.

In this paper, we will present a method that maps XML data into relational tables. Our method is still range based, which means it can process queries with regular path expression efficiently. But with the introduction of node grouping, the extra space needed for the indexing is reduced significantly. With fewer tables created, we will show that query processing can also be significantly expedited.