An XML querying method and system for constructing an XQuery/XPath query to a schema variable XML document. The method includes: receiving the query from a client computer; generating a tree structure; and generating, by query rewriting, an XQuery/XPath for the XML document based on the tree structure and configurable query constraints. The system includes: a tree structure generating unit for generating a tree structure; and a query writing unit for generating an XQuery/XPath query for the XML document based on the tree structure and configurable query constraints.