Namespaces are here for avoiding the naming conflicts and for readability. Unfortunately, they can't be used when declaring properties that kind of kills half of the namespace usefulness and forces you to either import everything into the global namespaces or forget the type system and work around with variants.

Example:

import QtQuick 1.0 as QtLib

QtLib.Rectangle {
    width: 400
    height: 300

    //the following doesn't work
    property QtLib.Rectangle fullyQualifiedProp: null

    // the following works
    property variant varProp: QtLib.Rectangle {}
}