Ed - the weight example is a good one, but obviously I can't present that as a use case, since we're dealing with dates, not weights, and offhand I can't think of a date analogy to a scale. Can you come up with an analogous use case for dates.
> -----Original Message-----
> From: Discussion of the Developing Date/Time Standards
> [mailto:[log in to unmask]] On Behalf Of Edward C.
> Sent: Thursday, October 22, 2015 12:15 PM
> To: [log in to unmask]
> Subject: Re: [DATETIME] Extended Interval (L2 )
> On Thu, 22 Oct 2015 09:44:27 -0400, Denenberg, Ray wrote
> > I also have difficulty explaining the difference between 'xx' and 'uu':
> > http://www.loc.gov/standards/datetime/pre-
> > ion "Note the difference in semantics between 'x' and 'u'. '196x' has
> > decade
> precision while '196u' has year precision. Both represent an unspecified year
> during the 1960s, but for 196x the year is not supplied because it is known
> only with decade precision. In contrast, for 196u the year is not supplied for
> reasons that are not specified but there is some expectation (though no
> guarantee) that the year may be supplied later; for 196x there is no such
> That does sum it up. What is so hard? Instead of dates/time I think we are
> better off thinking of temperature or weights. They are an area where I think
> we are much more accustomed to thinking in precision.
> How much does the object weigh? 2x grams versus 2u grams. The former
> means that the object weighs on a scale that can only read 10g (say a
> balance where we have only 2 nickels to measure against, e.g. 2x5g objects).
> That later says that we guess it is around 20-29 grams but expect to measure
> it with a gram scale and finalize its value..
> How do we in weights specify gram precision? 2g How do we specify that
> something is 2g measured to mg precision? 2.000g And 2g to centigram
> precision? 2.00g
> In weights.. The number 1xx means I've tagged the weight as some weight in
> the range 100 to 199 and expect to fill in the numbers once I place them on
> the balance. The x is just a placeholder for missing infomation.
> The number 1uu means something else..
> In weights and lengths we have units to help with our specification. ng, mg,
> g, hg, kg, ton, etc. and nm, mm, cm, m, km, hm, km,....
> 1uu mg is really 1 g.
> 1xx is NOT 1g.
> In scientific expressions we have +- to specify precision since not everything
> fits in 10s.
> In time we have ns, ms, s, min., hours, days etc.
> But what do we have with days? Months? Years? Decade, Century,
> Milennium, ..
> When someone says "gosh I have not eaten one of those for a decade" they
> don't mean that the last time they ate one was exactly 315576000 seconds
> Now the tricky bit and pop-quiz!
> uu is a century
> xu is a decade in a to be specified decade and xx is a year in a to be specified
> year and decade.
> What does "ux" mean?
> > However I'm going to try to defer that discussion for now.
> > Thanks.
> > Ray
> Edward C. Zimmermann, NONMONOTONIC LAB