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Re: Details of dateTime operations

From: Steve Harris <steve.harris@garlik.com>
Date: Fri, 3 Dec 2010 14:41:10 +0000
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
Message-Id: <E760E91F-E857-4996-A371-25F273DBFF98@garlik.com>
To: Andy Seaborne <andy.seaborne@epimorphics.com>
On 2010-12-03, at 14:12, Andy Seaborne wrote:

> Easier (hopefully!)
> 
> YEAR, MONTH, DAY, HOURS, MINUTES
>  Return an xsd:integer.
> SECONDS
>  Return an xsd:decimal (fractional seconds possible).

Sounds good.

What about a NOW()? Returning an xsd:dateTime for the current time, in the Z timezone. e.g.

CONSTRUCT {
  <new> dc:date ?now ;
        dc:title "new object" .
}
WHERE {
  BIND(NOW() AS ?now)   # will that work?
}

Very useful for batch processes and the like.

No strong feelings about TIMEZONE, we do everything in zulu time, so no practical experience.

- Steve

> TIMEZONE is a bit different.  In F&O it returns an xs:dayTimeDuration. There are operations like fn:timezone-from-dateTime for each of dateTime, date and time. See also casting rules [1].
> 
> xs:dayTimeDuration isn't a datatype we currently require support for - or xsd:duration - this affects the operations of "<" etc. dayTimeDuration is totally ordered [2].
> 
> F&O had accessors for xs:duration for years...seconds.
> 
> 1: Is xsd:dayTimeDuration the appropriate choice for SPARQL?
> 
> 2: If there is no timezone, what do we return? (we don't have the empty sequence, which is what F&O returns.)
> 
> 3: If it is going to be a duration, should we document that HOURS, MINUTES, SECONDS also apply to durations (AKA partial support)?
> 
> (Durations drop a bit of information : writing "00:00" or "Z" yield a duration of zero and you can't tell which because it's value based.  May matter if you care about round tripping.)
> 
> 	Andy
> 
> [1] http://www.w3.org/TR/xpath-functions/#casting-to-datetimes
> [2] http://www.w3.org/TR/xpath-functions/#duration-subtypes
> 

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Received on Friday, 3 December 2010 14:41:46 GMT

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