typeid element in UCN output

Hi,

I've recently noticed the relatively new addition of the 'typeid' 
element in UCN output such as:

<message type="error" ref="http://example.css">
     <context line="10">.clearfix</context>
     <title>Parse Error {*zoom:1;</title>
     <typeid>generator.unrecognize</typeid>
</message>

I'll find this very useful in being able to categorise validation errors.

Before I start depending to heavily on it being present in validation 
results, can I just check that this is a permanent addition to the UCN 
output and not just a temporary or experimental feature?

Kind regards,
Jon Cram

p.s. As an aside, does anyone know why the the UCN output format is so 
named?