private void expandImportList(String namespace, Vector namespaceList) {
        SchemaGrammar sg = fGrammarBucket.getGrammar(namespace);
        // shouldn't be null
        if (sg != null) {
            Vector isgs = sg.getImportedGrammars();
            if (isgs == null) {
                isgs = new Vector();
                addImportList(sg, isgs, namespaceList);
                sg.setImportedGrammars(isgs);
            }
            else {
                updateImportList(sg, isgs, namespaceList);
            }
        }
    }