With <oXygen/> you can validate your documents before using them in your transformation scenarios. The validation uses the Saxon 8.7.1 B processor or the 8.7.1 SA, eXist, Berkeley DB XML or X-Hive/DB if you installed them. This is in conformance with the XQuery Working Draft http://www.w3.org/TR/xquery/. The processor is used in two cases: validation of the expression and execution. Although the execution implies a validation, it is faster to syntactically check the expression without executing it. The errors that occurred in the document are presented in the messages view at the bottom of editor window, with a full description message. As with all error messages, if you click on one entry, the line where the error appeared is highlighted.
Please note that if you choose a processor that doesn't support XQuery validation you will receive a warning when trying to validate.
The Validate toolbar provides a button for quick access to the XQuery options in the <oXygen/> user preferences.