M-label definition

[Paul Hoffman]

At 11:17 PM -0400 4/3/09, John C Klensin wrote:
>	"An M-label is a string that becomes a U-label after
>	mapping but it not, itself, a U-label.   In more recent
>	terminology, if a U-label is a canonical form, the
>	M-label is a non-canonical form of the same thing.  The
>	categories of M-label and U-label are disjoint."
>	(Patrik and others)
>	
>	"An M-label is a string that can be mapped into a
>	[valid] U-label.  It may be a U-label, since those
>	trivially map into themselves.  The category of U-label
>	is a proper subset of the category of M-label." (Mark
>	and others).

I prefer the second one.