MIPs at control level

Hi all,

I have been reconsidering MIPs at control level recently.

First of all, the well-known trick ".[relevance_predicate]" should 
better be explicitly written with a @relevant attribute.

When a trigger has to be grayed on a specific condition, instead of 
having to create some element in some "work" instance, it would be nicer 
to just add a @readonly attribute.

Even @type might be useful for overwriting the effective data type 
because, for example, for a date of birth, using a not-constrainable 
date widget is not as convenient as a simple text input.

What do you think?

--Alain