Re: [Xmlastro-discussion] It's about time.

[Don W. <don...@ma...>]

>
>
> I introduced restricted versions of xs:datetime, xs:date, and
>xs:time to control the time zone option. I feel that observers should
>always include time zone information unless they are specifically
>recording a local time. I provide different elements for local times to
>distinguish them from "absolute" times
>
I don't see that. I would expect timezone information to be included 
specifically with local times (LST).
If you're using LAT or LMT I'd expect geographical information to be 
included.

Anyway I'm not so sure about all these formats.
If I want to include time information of the observation I'd expect at 
least LST or JD and preferrably UTC.
Should we make one of these time formats required and the others LAT, 
LMT,... optional?
For times included in a position LAT or LMT should not even be allowed 
to be included in the time information.
At least that is my opinion.

>It will be common, I think, for a set of observations to occur at
>different times on the same date. Note that the time zone information is
>inherited by the observation as well as the date.
>
I'm sure if we should do this. Timezone information is not that much, so 
it shouldn't be to much of a problem to include it in every local time 
(LST). It will make the information more readable.

>I propose allowing serveral local time forms. I'm not sure how necessary
>that is, but it seems easy so I figured we might as well. Local times do
>not carry any time zone information (nor can they). By definition, time
>zones don't make sense on a local time. Does that sound right?
>
Maybe we should include geographical information?

>The XML Schema time types require quoting times to 1 second precision.
>Obviously that makes no sense in many cases. To deal with that I propose
>adding a "resolution" attribute to our datetime elements to give document
>authors the ability to specify how significant their datetimes are.
>
><datetime resolution="P3H30M">
>  <ISO>2003-03-30T10:00:00-05:00</ISO>
></datetime>
>
>Here a duration of 3h30m is supposed to mean that the actual time is
>between +/-1h45m of the quoted time. I haven't played with xs:duration
>before but I think that's the right format for it.
>
I agree.

>All of this needs to be tested, of course, before putting it into the
>schema officially. However, before going that far... is this the right
>track or am I totally off base?
>
You're on the right track.
I'm not so sure about all those local time formats. If you don't include 
geographical information those times will be meaningless to most 
observers. You cannot calculate the 'absolute' time.
I can see that you might want to include this information though. But 
should it be part of the basic time information which will be included 
in positions and observations?

Don