If you need to validate an XSLT stylesheet with a validation engine that is different from
the built-in engine, you can configure external engines as custom XSLT validation engines in
the Oxygen XML Editor preferences. After a custom validation engine is properly configured, it can be
applied on the current document by selecting it from the list of custom validation engines in
the 
Validation toolbar drop-down list. The document is validated against the
schema declared in the document.
There are two validators that are configured by default:
- MSXML 4.0 - included in Oxygen XML Editor (Windows edition). It is associated to the XSL Editor type in Preferences page.
- MSXML.NET - included in Oxygen XML Editor (Windows edition). It is associated to the XSL Editor type in Preferences page.