private Map<String, Class<?>> loadExtensionClasses() {
		final SPI defaultAnnotation = iFaceType.getAnnotation(SPI.class);
		if (defaultAnnotation != null) {
			String value = defaultAnnotation.value().trim();
			if (value != null && value.length() > 0) {
				if (defaultExtensionName == null) {
					defaultExtensionName = value;
				}
			}
		}

		Map<String, Class<?>> extensionClasses = new HashMap<String, Class<?>>();
		loadExtensionFile(extensionClasses, TRIPLE_EXTENSION_DIRECTORY);
		return extensionClasses;
	}