Qt Declarative is a runtime interpreter that reads the Qt declarative user interface definition, QML data, and displays the UI that it describes. The QML syntax allows using JavaScript to provide the logic, and it is often used for this purpose. It is not the only way, however: logic can be written with native code as well.[2]
Qt Quick and QML are officially supported in Qt 4.7 (with Qt Creator 2.1),[3] and it is a commercial option in mobile applications when Qt 4.7 is available for deployment in Symbian and Maemo and MeeGo devices. It is also the native language of Ubuntu Touch.[2]