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Re: Requirement for 'Valid Time'

From: Frans Knibbe <frans.knibbe@geodan.nl>
Date: Wed, 11 Nov 2015 14:41:53 +0100
Message-ID: <CAFVDz41n8a=H6tttwRcxKhKZUeboR1BVwJJjk6cwtVpeZ2XBmA@mail.gmail.com>
To: "public-sdw-wg@w3.org" <public-sdw-wg@w3.org>
Cc: Simon Cox <Simon.Cox@csiro.au>, "Tandy, Jeremy" <jeremy.tandy@metoffice.gov.uk>, "Kerry Taylor (Kerry.Taylor@acm.org)" <Kerry.Taylor@acm.org>, "Little, Chris" <chris.little@metoffice.gov.uk>
Thanks to Chris for continuing the discussion. My comments are inline:

2015-11-10 17:47 GMT+01:00 Little, Chris <chris.little@metoffice.gov.uk>:

> Dear colleagues,
> Unfortunately, tomorrow I will be travelling by train, with rubbish phone
> connections, so it will be highly unlikely that I can join in, so I will
> add my views on UCR-16 here:
> 1. I agree that 'Valid Time' is outside the scope of the Time OWL
> ontology, as are lots of other time semantics (verification time, time of
> last update, creation time, publication time, etc).
> 2. There are widely used ontologies that recognise different kinds of time
> e.g. Dublin Core.
> 3. It seems to be out of scope for spatial data as opposed to just 'data
> on the Web'. However, there are lots of examples in the spatial domain,
> such as environmental observational data and weather forecasts.
> Increasingly, to know a location, one needs to know when.

True, but that by itself does not warrant us adopting this requirement.
Examples of many aspects of handling data can be found in the spatial
domain, but that does not mean we should consider working on them. Why make
an exception for this particular example?

> 4. The Met Ocean Domain WG of OGC produced a Best Practice profile of the
> OGC WMS1.3 standard to capture some of these time concepts and improve
> interoperability arising from real world experience of interoperability
> problems. The BP gave a standard name for these non-standard time semantics
> ("Reference Time").

As I see it, OGC semantics form a more or less closed system. Other than
very basic data types they can not rely on semantics that are defined
outside of the system. Hence the need to standardise aspects of reality
that are not strictly spatial in the OGC. But since the SDWWG is acting in
a web environment, it should be OK to have to rely on semantics that are
defined somewhere out of our sphere of control.

> 5. I do not know if there is a generic 'framework' for capturing different
> time application level semantics in Data on the Web.
> 6. I think this is important for enough SDWWG Use Cases that it should not
> be ruled out of scope unless some other 'owner' is identified to take it
> forward.

Yes, we could take it upon ourselves to make some other party the problem
owner. But that would be something very different from taking it upon
ourselves to work on semantics for valid time.

This remark has led me to see the resemblance between ISSUE-16
<https://www.w3.org/2015/spatial/track/issues/16> and ISSUE-11
<https://www.w3.org/2015/spatial/track/issues/11>. There was a risk of
having a requirement that would make us have to deal with the semantics of
provenance. Now the provenance requirement
that we should seek alignment of our work with existing standards for
provenance. I believe that issue was resolved to everyone's satisfaction.

In this case we could go the same way: have a requirement for OWL Time that
says that the work should be aligned with existing methods of expressing
valid time. That way we do acknowledge that valid time is important for
spatial data, but we do not make it a primary responsibility for us to have
semantics for valid time.

This could lead to a requirement like:

"Ensure alignment with existing methods for expressing the time in which
data are valid (e.g. http://purl.org/dc/terms/valid)."

In this case the appropriate related deliverable would be only OWL Time.


> HTH, Chris
> Chris Little
> Co-Chair, OGC Meteorology & Oceanography Domain Working Group
> IT Fellow - Operational Infrastructures
> Met Office  FitzRoy Road  Exeter  Devon  EX1 3PB  United Kingdom
> Tel: +44(0)1392 886278  Fax: +44(0)1392 885681  Mobile: +44(0)7753 880514
> E-mail: chris.little@metoffice.gov.uk  http://www.metoffice.gov.uk
> I am normally at work Tuesday, Wednesday and Thursday each week
Received on Wednesday, 11 November 2015 13:42:30 UTC

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