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[[Category:Meeting]]
= Agenda for SDWWG teleconference [http://www.timeanddate.com/worldclock/fixedtime.html?msg=SDWWG+Call&iso=20160217T20&p1=1440&ah=1  17 February 2016 20:00 GMT]=
*Chair: Ed
*Scribe: TBA
*Regrets:
::::Recurring: 
::::This meeting: Clemens,Andreas, Lewis, Lars
== Preliminaries ==
# Check bots are running (see below)
# Matching everyone on IRC and Webex: Each person should type 'present+ ' followed by their name. 
# Appoint Scribe. Scribe should enter 'regrets+ ' followed by the names of people who have sent regrets (ideally by adding their own name to this page)
# Approving [http://www.w3.org/2016/02/03-sdw-minutes.html last meeting's minutes] 
# [[Patent Call]]

== Main agenda ==
# Short update on last weeks Face to Face
# Coordination with DWBP See [https://lists.w3.org/Archives/Public/public-sdw-wg/2016Feb/0060.html homework]
# Temporal Issues [as added by Chris Little, following F2F3]
    
* Accuracy versus Precision confusion is made worse by the only widely accepted temporal notation (ISO8601) which often conveys unjustified precision. E.g. A document update time of 2016-02-16T00:00:00Z is highly unlikely to imply that the document was updated at precisely midnight UTC.

* Numerous software artifacts conflate times and dates, and sometimes mistakenly assume dateTime objects can be used as a coordinate reference system.

* The current ISO8601:2004 standard states that the notation is meant to reflect an underlying Gregorian calendar, with leap seconds. Many occurrences of apparent ISO8601 timestamps ignore leap seconds and the tens of seconds difference between legal civil time and GPS time. Many people refer to the oboslete ISO8601:1988 as it is publicly available, whereas the current version has to be bought.

* There is an assumption that in this age, computer times, such as from a system log with IETF RFC 3339 timestamps, are comparable with sub-second precision. Even when NNTP protocols have been correctly implemented, this is difficult to achieve.

* Some countries only switched to the Gregorian calendar as late as the 1920s, so historical documents from between 1588 and 1923 may be several days adrift, depending on the country, giving inaccuracy in data extraction.

* There are many other calendar systems in use, and there is no agreed notation as to which is used, never mind agreed and accurate algorithms for their implementation. There is a rough categorisation of calendars into those that can be related directly to the Gregorian, because they are algorithmically based, and those that are fundamentally observation based, with a precision of minutes or even days.

* Overlying temporal ontologies may not allow valid reasoning if the underlying temporal 'microformats' are not accurate at the appropriate level.

* There is now an OGC Standards Working Group to produce standardised WKT (Well Known Text) to specify non-Gregorian calendars (e.g. no leap seconds, or no leap days, or 360 days/year, etc).

* There is a SDW WG proposal to minimally enhance the OWL Time vocabulary with non-Gregorian calendars.


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==Annotations==
* [[Type::Telecon]]
* [[Subject::DWBP Coordination]]
* [[Date::2016-02-17]]
* [[Minutes::http://www.w3.org/2016/02/17-sdw-minutes]]
* [[Scribe:: Kerry]]

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Minutes	http://www.w3.org/2016/02/17-sdw-minutes +
Scribe	Kerry +
Subject	DWBP Coordination +
Type	Telecon +
Date "Date" is a type and predefined property provided by Semantic MediaWiki to represent date values.	February 17, 2016 +

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