question: public void registerExtension ( ExtensionNamespaceSupport extNsSpt ) { String namespace = extNsSpt . getNamespace ( ) ; if ( namespaceIndex ( namespace , m_extensions ) == - 1 ) { m_extensions . add ( extNsSpt ) ; if ( m_unregisteredExtensions . contains ( namespace ) ) m_unregisteredExtensions . remove ( namespace ) ; } }
target:  Register the extension namespace for an ElemExtensionDecl or ElemFunction, and prepare a support object to launch the appropriate ExtensionHandler at  transformation runtime.