A computer readable medium, method, and device for generating eXtensible Markup Language (XML) schema fragments for use in validating an XML message in a particular wire format is disclosed. The method uses as its input a custom XML schema based message model containing logical model extensions or wire format specific rendering options. The output of the method is an XML schema that includes XML schema fragments. The output schema complies with an accepted XML schema standard recognized by a standard schema validator. At run time, the output XML schema, along with the standard schema validator, may be used at a node which does not understand the custom message model to validate incoming XML messages. Depending upon the manner of generating of the XML schema fragments, the resultant validation may be strict or lax.