On Mon, Jun 4, 2012 at 10:21 PM, Martin Davis <[email protected]> wrote:
> Here's a couple of data points for this discussion:
>
> http://mapserver.org/ogc/wms_time.html
>
> MapServer has addressed this issue (see the section Interpreting Time
> Values), but they seem to do different things depending on the back-end data
> source.  For PostGIS at least they use the "time as time window" approach,
> by virtue of using the DB date_trunc function, which amounts to the same
> thing).  One takeaway from this: I would suggest we want a data
> source-independent strategy.
>
> http://augusttown.blogspot.ca/2010/03/two-ambiguities-about-time-in-ogc-wms.html
>
> This blog post discuss the issue, and weighs in on the side of treating all
> time values as time windows (with duration determined by precision).  This
> seems to make sense to me.  Although, what then is meant by a TIME of
> 2012-06-01/2012-06-02".  Is that the window including exactly June 1, or
> does it include June 1-2 ?

I agree the time window approach makes sense, and yes, the current
implementation
switches to a interval only if you explicitly ask for an interval,
otherwise the time
elements missing are assumed to be zero (from memory, at least).

It may be an easy fix, inside the time kvp parser, if the time is not
fully specified
turn it into a interval?
We already handle t1/t2 as an extension to the wms spec (which would ask for
a third parameter, the period).

However... how do we handle a list of values that have no full precision?
Turn it into a list of intervals? Now, this we don't handle...

Cheers
Andrea

-- 
Ing. Andrea Aime
GeoSolutions S.A.S.
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