[oXygen-user] XInclude Validation Errors

Utilizing oXygen 5.1 with Docbook 4.4b2 DTD and XSL 1.67.2 with the default oXygen Xalan transformer. A document validation check produces the following error: Element type "xi:include" must be declared along with a couple of related error messages. XInclude Processing is enabled utilizing Options | Preferences | XML Parser Options Docbook files compile correctly utilizing XInclude but the errors during the document validation are irritating. Please advise. -- Ray Miller