The XQL (XML Query Language) is a notation designed to address XML documents just as SQL is used to access relational databases. XQL Query Engine release 1.1(XQE1.1) is a JAVA 1.2 compliant API package that implements the XQL specifications for XML document addressing. It offers the capabilities of processing XQL query statements, accessing entities contained in XML documents and return results to calling applications.

The XML Query Language proposal (XQL), jointly developed by Texcel, webMethods, and Microsoft, proposes a query language for XML documents. This document complements the proposal by describing XQL's underlying design and the motivation for that design.

As more and more information is either stored in XML, exchanged in XML, or presented as XML through various interfaces, the ability to intelligently query our XML data sources becomes increasingly important. XML documents are structured documents – they blur the distinction between data and documents, allowing documents to be treated as data sources, and traditional data sources to be treated as documents.