Schema validation

can someone pls explain what the following sentence in the schema guide means. This pertains to the conformsTo parameter that is supplied in a schema:validate service

“The specified schema is used only for validating nodes with “Names” that are not from XML Namespaces (that is, nodes with XML Namespace URI = null).”

Does this imply that if an xml instance uses namespaces, it cannot be validated using this built in flow service??? !!!