Hi all:
Another thing to consider is the relationship to the current udunit/CF
standard for specifying dates in the unit string
"period SINCE date"
The udunits documentation
<
http://www.unidata.ucar.edu/software/udunits/udunits-2/udunits2lib.html#Grammar>
not being very clear, I wrote up my understanding of current practice here:
http://www.unidata.ucar.edu/software/netcdf-java/CDM/CalendarDateTime.html#ISO_String
Note the paragraph towards the end starting with "with the following
differences, to allow backwards compatibility with udunits:"
as this documents the differences AFAICT that current practice has with
ISO 8601 standard.
It appears that this grammer is slightly more lenient than the one that
Aleksandar proposes.
John
On 3/19/2013 6:21 PM, Dave Allured - NOAA Affiliate wrote:
> Aleksandar,
>
> I support this standard name proposal. I like the restrictions on
> syntax and use to a sensible subset for scientific applications.
>
> Unlike most standard name proposals, this is more than a simple
> definition of a physical meaning. You are making a set of technical
> use specifications, with significant departures from the reference
> standard ISO 8601. Will there be a reference archive for the
> particular specifications? Will this reside exclusively in the CF
> standard name table, or in a new CF chapter or appendix, or something?
> I think there needs to be something better than "that CF list
> discussion of January to March 2013".
>
> Please be exact in the specification of the reference calendar. Try
> to eliminate all possible measurement ambiguities. Leap seconds are a
> problem. There are no leap seconds in the standard calendars
> currently defined by CF, and I was not able to locate exactly where
> ISO8601 stands on this issue. I would really hate to see a "Gregorian
> calendar" or proleptic_gregorian implementation with interval
> calculations that differ from the CF defined calendars.
>
> I suggest a requirement that the calendar attribute be included on all
> variables using datetime_iso8601. If leap seconds are excluded, then
> the correct attribute value should be "proleptic_gregorian".
>
> You have "four-digit years". Are you explicitly restricting the spec
> to only years 0000 through 9999?
>
> Thank you for working on this!
>
> --Dave
>
> On Fri, Jan 11, 2013 at 10:00 AM, Aleksandar Jelenak - NOAA Affiliate
> <aleksandar.jelenak at noaa.gov> wrote:
>> Dear All:
>>
>> Here's the modified proposal for the datetime_iso8601 standard name:
>>
>> standard_name: datetime_iso8601
>>
>> Units: N/A
>>
>> String representing date-time information according to the ISO
>> 8601:2004(E) standard. Variables with this standard name cannot serve
>> as coordinate variables. Date-time information is in the Gregorian
>> calendar. For dates preceding the Gregorian calendar the date-time
>> information is in the proleptic Gregorian calendar. Possible date-time
>> string forms are:
>>
>> <datetime> = <date> "T" <time> <timezone> ;
>>
>> <date> = YYYY "-" MM "-" DD | YYYY "-" DDD ;
>>
>> <time> = hh | hh ":" mm | hh ":" mm ":" ss | hh ":" mm ":" ss "." S
>> | hh ":" mm ":" ss "," S ;
>>
>> <timezone> = "" | "Z" | "+" hh | "+" hh ":" mm | "-" hh | "-" hh ":" mm
>>
>> Where:
>>
>> * "YYYY" is a four-digit year (0000-9999).
>>
>> * "MM" is a two-digit month of the year (01-12).
>>
>> * "DD" is a two-digit day of the month (01-31).
>>
>> * "DDD" is a three-digit ordinal day of the year (001-366).
>>
>> * "hh" is a two-digit hour (00-23).
>>
>> * "mm" is a two-digit minute (00-59)
>>
>> * "ss" is a two-digit second (00-59).
>>
>> * "S" is one or more digits representing a decimal fraction of the
>> second.
>>
>> * The value of any designator when not specified is zero.
>>
>> * If <timezone> is ommitted the default value is "Z".
>>
>>
>> -Aleksandar
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Received on Wed Mar 20 2013 - 08:09:00 GMT
