On Fri, 26 Nov 2010 09:09:20 +0000, Simon Grant wrote

> Having separated out the "guesstimate" as something we might agree on
separately, I *think* the rest of this position is compatible with having just
one representation, not two. Operationally, pragmatically, I cannot see a
difference in a value as presented. The difference as expressed here is to do
with future intentions, and I don't believe we should be attempting to
represent anything to do with future intentions. 

Its not a guess.. Just an expression of uncertainty.


1959-12-25 means the event took place on 25 Dec 1959 (its unit of precision is
1 day) 
1959-12 means the event took place in Dec. 1959 (its unit of precision is month) 
1959 means the event took place in 1959 (its unit of precision is the year) 
195u means the event took place in the 1950s (its unit of precision is 10 years) 
19uu means that the event took place in the 20th century (its unit of
precision is 100 years) 
1uuu means that the event took place in the second milennia (its unit of
precision is 1000 years) 
uuuu means that we don't know when the event took place

The above uses of u we could address with a (implicit) specification of
Instead of 195u we could say "1950s" 
Instead of 19uu we could say "20th century" 
Instead of 1uuu we could say "Second milennia" 
Instead of uuuu we could say "Date unknown"

But the 'u' delivers more:

uu59 means that we know the event took place in the year 59 but don't know the
1u59 means that we know the event took place in the year 59 in the second
milennia but don't know which century. 
uuu9 means ... 
[above: implicit year precision]
[decade precision]
[century precision]

Notice the great difference between saying an event took place in the "1950s"
and saying that the event might have taken place in 1950 but one is not sure?

195u might not contain (1959)?

In what year did the Great Flood start? When did it end (well it lasted a full

We may specify a year precision. Perhaps even a time.. but ..

> However, in both cases this states a claim or belief that the actual value
is one of the set running all the way from 1980 to 1989. I don't see any
*pragmatic*, *operational* reason for making a distinction. Furthermore, I
believe that if such a distinction were made, in practice people would argue
over or confuse the two, leading to inconsistency of semantics. The
consequence would be that in practice, both forms would have to be treated
equally in any case. 

The extended date system has not provision at this time for |. 

In our systems (matching and searching dates) we would all probably handle
them as the same but the sentence

But.. just to hammer this into the ground...

195u is expressing something known (1950s) 
195| is expressing more: Not only is it known that the event took place in the
1950s but we claim to be able (at some future time) to increase the precision. 

195| is essentially claiming a year precision but expressing that the year is
not yet collected. Its a kind of "volatile" flag announcing that the precision
might increase at some future time.

[Personally in my search engine--- main application for my date class-- I
have only precision so can't handle all the possible combinations, e.g. 195u
would be OK to search a date object index but I can't see myself at this time
handling searches for 19u6 except as glob searches against the text where the
date was encoded, e.g. date=19?6 ] 

> We could be crazy and add grade of certainty and data-quality: 
> [...] 
> Thanks, but I agree this looks crazy enough to leave well alone. Simon 
> -- 
> Simon Grant 
> +44 7710031657 


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