Customizing Assert Error Messages

To customize the error messages that the Xerces or Saxon validation engines display for the <assert> and <assertion> elements, set the @message attribute on these elements.

• For Xerces, the @message attribute has to belong to the http://xerces.apache.org namespace.
• For Saxon, the @message attribute has to belong to the http://saxon.sf.net/ namespace.

The value of the @message attribute is the error message displayed if the assertion fails.