FileResourceManager frm = FileResourceManager.getInstance();
File unzippedRoot = frm.unzipFileResource(res);
//with VFS FIXME:pb:c: remove casts to LocalFileImpl and LocalFolderImpl if no longer needed.
VFSContainer vfsUnzippedRoot = new LocalFolderImpl(unzippedRoot);
VFSItem vfsQTI = vfsUnzippedRoot.resolve("qti.xml");
//getDocument(..) ensures that InputStream is closed in every case.
Document doc = QTIHelper.getDocument((LocalFileImpl) vfsQTI);
//if doc is null an error loading the document occured (IOException, qti.xml does not exist)
if (doc == null) return;