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On Fri, 15 Feb 2013 16:52:48 +0100, [UTF-8?]SaaÅ¡ha Metsärantala wrote
> Hello!
> 
> > "For time, is hour:minute:second sufficient, or do we need to support 
fraction of a second?"
> In the library / museum / archive world, expressing something similar to 
> "during the 1870'ies approximately" is often a more useful feature than a

The two are hardly exclusive. I think I've been quite strong in voicing my 
position on precision/readability and data reliability/repeatability.
Decade, century or .. "precision" is no different than minute, second, 
millisecond, nanosecond,... "precision". 

> precision at the millisecond's level. This is one of the reasons why there 

Millisecond is a decimal model of precision. There are others.

The Jewish time model is an example of a non-decimal time model that is 
currently widely used. 

Jews all over the world use a time with a precision of 1/72 a time degree 
(Halokim) or  3 1/3 seconds (1/18 minute). The precision of the date/time for 
events such as new month (defined by moon) is 3 1/3 seconds.

Just as we have ..., decade, year, month, day, hour, minute, second, 
millisecond,... models in the ISO world we have also ...,day, hour, minute, 
halokim, regaim (76 regaim = 1 halokim) in the Jewish ... (to make things even 
more complicated the time for lunar festivals is the time of the event in 
Jerusalem)

Since hour, minute, second are based on degrees and are not decimal (60 
seconds= 1 minute, 60 min= 1 hour, 24 hours = 1 day) to demand that the minute 
be divided by tens is a break in design---- the Napoleonic system went the 
other way to define 1 year = 10 months, 1 day = 10 hours, 1 hours = 10 ...)

> was a need for EDTF and the reason why we focused on approximations (and 
> other features) more than fractions of seconds.
> 
> If you consider it is useful (and it may probably be useful in some 
> cases), it is OK for me to add this feature in EDTF. It is quite easy to 
> modify the BNF for that and there should probably not be major problems to 
> implement a parsing taking fractions of seconds into account. There are 
> several more crucial (but also more difficult to describe and implement) 
> features to be added to EDTF and I consider that fractional seconds is not 
> a priority, but I consider it is OK to add this feature at level zero, 
> remembering that it is part of xsd:dateTime
> http://www.w3.org/TR/xmlschema11-2/#con-dateTime-day to which I suggest to 
> stick. Let's keep in mind though, that according to
> dotat.at/tmp/ISO_8601-2004_E.pdf (page 16) ISO_8601 reads:
> 
> > "the decimal fraction shall be [...] the comma (,) or full stop (.). Of 
these, the comma is the preferred sign."
> 
> and
> 
> > "a decimal fraction of hour, minute or second may be included."
> 
> whereas xsd:dateTime only allows dots (full stops) as separators and only 
> allows fractional seconds (not fractional hours nor fractional minutes).
> 
> This should not be a problem though, because EDTF level zero is defined as 
> a profile of ISO_8601.
> 
> Regards!
> 
> [UTF-8?]Saašha,


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Edward C. Zimmermann, NONMONOTONIC LAB/BSn
http://www.ibu.de/IB_Engine
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