#### XML hierarchical logic in relational schema

The XML hierarchical logic will be maintained in the transformed relational schema. The parent-child relationship in the XML schema can be maintained by the following two ways:

- If the parent and children nodes are transformed to different tables, the parent-child relationship will be maintained by primary key and foreign key in tables, and this relationship can be reproduced by applying the join of the primary key and foreign key.
- If the children nodes can be transformed to columns, the parent-child relationship in the XML hierarchical logic will be maintained in the including relationship of table-column.