protected void resolveKeyRefs() {
        for (int i=0; i<fKeyrefStackPos; i++) {
            XSDocumentInfo keyrefSchemaDoc = fKeyrefsMapXSDocumentInfo[i];
            keyrefSchemaDoc.fNamespaceSupport.makeGlobal();
            keyrefSchemaDoc.fNamespaceSupport.setEffectiveContext( fKeyrefNamespaceContext[i] );
            SchemaGrammar keyrefGrammar = fGrammarBucket.getGrammar(keyrefSchemaDoc.fTargetNamespace);
            // need to set <keyref> to hidden before traversing it,
            // because it has global scope
                DOMUtil.setHidden(fKeyrefs[i], fHiddenNodes);
            fKeyrefTraverser.traverse(fKeyrefs[i], fKeyrefElems[i], keyrefSchemaDoc, keyrefGrammar);
        }
    }