public Grammar retrieveGrammar(XMLGrammarDescription desc) {
            if (desc.getGrammarType() == XMLGrammarDescription.XML_SCHEMA) {
                final String tns = ((XMLSchemaDescription) desc).getTargetNamespace();
                if (fGrammarBucket != null) {
                    Grammar grammar = fGrammarBucket.getGrammar(tns);
                    if (grammar != null) {
                        return grammar;
                    }
                }
                if (SchemaSymbols.URI_SCHEMAFORSCHEMA.equals(tns)) {
                    return SchemaGrammar.Schema4Annotations.INSTANCE;
                }
            }
            return null;
        }