Canonical lexical representation of duration, redux

On 2002-11-03, John Mercado asked what the canonical lexical
representation of duration is; Malhotra replied that there is no
need to specify it, since there is only one lexical representation
per value.  This reply seems to contradict the recommendation:

	If the number of years, months, days, hours, minutes,
	or seconds in any expression equals zero, the number
	and its corresponding designator may be omitted.
	                                    [section 3.2.6.1]

Thus, for example, "P1Y" and "P1Y0M" are alternative lexical
representations for the same value.  Furthermore, according to
erratum E2-23, leading zeroes are permitted in each field, making
"P01Y" a third alternative.

Mercado's question is pertinent.

-- 
Steven Taschuk           | Receive them ignorant;
staschuk@telusplanet.net | dispatch them confused.
                          |   (Weschler's Teaching Motto)