DR033: UI interactions

<DR033>
Requirement that doesn't preclude UI interactions but should not define that
UI. 
Issue (i.033.01):

Do things put in XP should be human friendly or should it be possible to use
more human friendly or allow interaction with human.
</DR033>

I think the original motivation for this requirement was to allow messages
to be sent to devices and have those messages drive some UI.

Vis issue i.033.01: I think that should be a separate requirement.  Perhaps
introduce something like <annotation> from XSD.

Comments?

Alex