Can you use qualified class-names in MXML?

Question

It's common to do something like:

<s:Application  xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:app="com.john.*"
        xmlns:ctrl="com.john.controls.*" >
    <app:MyView ... />
    <ctrl:MyControl ... />
</s:Application>

Is it a requirement/limitation of MXML I have to define xmlns:... for every namespace used? Or is there a syntax that lets me do things like:

<app.Controls:MyControl ... />
<com.john.controls:MyControl ... />

It just seems a pain to define a Xml namespace for every sub-namespace.