If you have written applications that are based on Software AG's query language X-Query and wish to migrate these applications to the W3C query language XQuery, guidelines for doing this are provided in the Release Notes document of the documentation set for Tamino XML Server version 4.2. You can find the documentation archive for version 4.2 at Software AG's web-based Product Support System, Empower (https://empower.softwareag.com/).