[georss] Time and Space

Carl Reed OGC Account creed at opengeospatial.org
Tue Feb 13 18:28:21 EST 2007 

Jumping in after reading the thread.

The discussion of maintaining simplicity and trying to figure out how to 
make georss more expressive is almost identical to the discussions that have 
gone on in the OASIS Emergency Management TC regarding how to encode 
location in a variety of new standards (approved and in process) for use by 
the emergency management committee. These standards currently use some 
fairly simple schema for encoding points, circles, and polygons. They will 
be upgrading the specs to use a new (draft) GML Oasis application schema. 
The basic information model is almost identical to georss (GML), although 
there are additional geometry types and so forth. The only reason that I was 
able to convince the OASIS TC to use GML was after they saw GeoRSS GML. They 
wanted something almost as simple but with more geometry types and some 
additional properties. But they also want to restrict the expressiveness 
that could be achieved by using GML because they want to maintain 
simplicity. So, for example, they do not want a generic approach for 
specifying units of measure for defining the radius of a circle. Kilometers 
in fine, thank you.

At the same time, they do want the ability to allow a CAP or EDXL message to 
reference "rich" geospatial content but without affecting the "core" spec 
anymore than required. Thus, for example, in EDXL-DE and RM you can specify 
by reference additional content, such as a GML payload that perhaps defines 
the geometry of a smoke plume, including time, date, info about the contents 
of the plume and so forth.

This is a very round-about way of suggesting that perhaps there is a general 
approach (solution) to being able to extent the information content 
available in a GeoRSS GML feed without corrupting the core GeoRSS spec and 
thus maintaining simplicity. If we cannot do this, than the issue of feature 
creep will come back again and again and again . . .

Just a thought.

Cheers

Carl

----- Original Message ----- 
From: "Ron Lake" <rlake at galdosinc.com>
To: "Knoth, Brian D." <bknoth at mitre.org>; "Mikel Maron" 
<mikel_maron at yahoo.com>; <georss at lists.eogeo.org>
Sent: Tuesday, February 13, 2007 3:56 PM
Subject: Re: [georss] Time and Space


> Could you give an example of this? - I would not use description since
> it is totally open ended!
>
> R
>
> -----Original Message-----
> From: Knoth, Brian D. [mailto:bknoth at mitre.org]
> Sent: February 13, 2007 11:02 AM
> To: Ron Lake; Mikel Maron; georss at lists.eogeo.org
> Subject: RE: [georss] Time and Space
>
> Ron,
>
> I believe that "role" of a geometry can already be conveyed within the
> existing GML geoRSS profile. There are description/name/metadata
> elements associated with every geometry at the abstract base level. I
> would think these elements could be used to pass additional information
> like role to consumers. Based off my previous example, here is what I
> am thinking (note: allowing multiple geometries within a where node):
>
>
> <item>
> <title>Flight 1995</title>
> <link>http://..flightdetails</link>
> <description>some desc</description>
> <guid
> isPermaLink="false">id:flight-0A05000760l02yz</guid>
> <pubDate>2006-03-02T20:36:12Z</pubDate>
> <georss:where
> xmlns:georss="http://www.georss.org/georss">
> <gml:Point
> xmlns:gml="http://www.opengis.net/gml">
>
> <gml:description>takeoff</gml:description>
> <gml:pos>30.8944
> -124.5270</gml:pos>
> </gml:Point>
> <gml:Envelope
> xmlns:gml="http://www.opengis.net/gml">
> <gml:description>turn point
> A</gml:description>
> <gml:lowerCorner>43.8944
> -123.5270</gml:lowerCorner>
> <gml:upperCorner>44.3444
> -122.9002</gml:upperCorner>
> </gml:Envelope>
> <gml:EnvelopeWithTimePeriod
> xmlns:gml="http://www.opengis.net/gml">
>
> <gml:description>rendezous</gml:description>
> <gml:lowerCorner>30.8944
> -107.5270</gml:lowerCorner>
> <gml:upperCorner>35.3444
> -108.9002</gml:upperCorner>
> <gml:timePosition
> indeterminatePosition="before">2006-03-02T21:30:00Z</gml:timePosition>
> <gml:timePosition
> indeterminatePosition="after">2006-03-02T21:40:00Z</gml:timePosition>
> </gml:EnvelopeWithTimePeriod>
>
> </georss:where>
> </item>
>
> Regards,
> brian
> ________________________________
>
> From: Ron Lake [mailto:rlake at galdosinc.com]
> Sent: Tuesday, February 13, 2007 11:32 AM
> To: Mikel Maron; Knoth, Brian D.; georss at lists.eogeo.org
> Subject: RE: [georss] Time and Space
>
>
>
> Mike:
>
>
>
> If you do that - allow multiple geometries inside a single
> "where" property - how does anyone know what they mean?  In GML a
> property (like where) is used to describe the role of the geometry -
> e.g.
>
>
>
>             <abc:centerLine>
>
>                         <gml:LineString> ... </gml:LineString>
>
>             </abc:centerLine>
>
>             <abc:position>
>
>                         <gml:Point>... </gml:Point>
>
>             </abc:Point>
>
>
>
> How does that work in GeoRSS?  How do you know the roles of
> Point and LineString otherwise?
>
>
>
> Cheers
>
>
> Ron
>
>
>
> ________________________________
>
> From: georss-bounces at lists.eogeo.org
> [mailto:georss-bounces at lists.eogeo.org] On Behalf Of Mikel Maron
> Sent: February 12, 2007 11:50 AM
> To: Knoth, Brian D.; georss at lists.eogeo.org
> Subject: Re: [georss] Time and Space
>
>
>
> Brian
>
> There was a thread on this last month that went into the issues
> .. http://lists.eogeo.org/pipermail/georss/2007-January/
>
> But I should've been more specific .. you can include any kind
> of GML payload in GeoRSS GML, which could have multiple geometries,
> but those all would be included in a single georss:where.
>
> -Mikel
>
>
>
> ----- Original Message ----
> From: "Knoth, Brian D." <bknoth at mitre.org>
> To: Mikel Maron <mikel_maron at yahoo.com>; georss at lists.eogeo.org
> Sent: Monday, February 12, 2007 7:41:39 PM
> Subject: RE: [georss] Time and Space
>
> Mikel,
>
>
>
> I'll take a look at your links in a moment, but just quickly
> wanted to respond to the issue of not being able to have multiple
> <georss:where> nodes under an <item>. I know that I read this
> restriction somewhere else and my only question is simply why not?  I
> don't know of any restriction defined in the RSS specification that
> limits child elements to only a single occurrence, is there?
>
>
>
> thanks,
>
> brian
>
>
>
> ________________________________
>
> From: Mikel Maron
> [mailto:mikel_maron at yahoo.com]
> Sent: Monday, February 12, 2007 2:38 PM
> To: Knoth, Brian D.; georss at lists.eogeo.org
> Subject: Re: [georss] Time and Space
>
> Hi Brian
>
> I'm very interested in incorporating time, visualizing
> and acting on change. Gave a presentation outlining some thoughts on
> this foss4g..
>
> http://www.foss4g2006.org/contributionDisplay.py?contribId=161&sessionI
> d=47&confId=1
>
> Like Raj, I think time could be seen as having wider
> application than just space. I've re-used the RSS and Atom
> time-oriented fields for some
> basic stuff.
>
> http://worldkit.org/doc/time.php
>
> For richer time specifications, there hasn't been
> agreement on a single encoding. Upcoming.org has a bit to say on this..
>
>
> http://community.upcoming.org/w/index.php/Nerdy_Questions#What_are_the_
> guidelines_you_follow_when_creating_RSS_feeds.3F
>
> They're using xCal. There's also an old RSS 1.0 module
> called Event .. http://web.resource.org/rss/1.0/modules/event/
>
>
> While writing this I just saw your followup. One thing
> about your usage, you can't associate multiple georss:where elements
> with a single item;
> it's a one to one relationship.
>
> Best
> -Mikel
>
> ----- Original Message ----
> From: "Knoth, Brian D." <bknoth at mitre.org>
> To: georss at lists.eogeo.org
> Sent: Monday, February 12, 2007 1:40:54 PM
> Subject: [georss] Time and Space
>
> Hi,
>
> I'm new to this mailing list, yet have been advocate of
> RSS and geoRSS
> on some internal projects for a while. I do have a few
> concerns with
> regard to real practical acceptance of geoRSS, yet, I
> understand the
> need to try and balance simplicity and expressiveness.
> As such, we are
> attempting to utilize GML geoRSS, however, we have
> needed to extend the
> GML geoRSS with the ability identify time as well as
> space.
>
> I wanted to just send out our approach to doing this to
> get comments
> from anyone else who might be interested in this on the
> mailing list.
> Simply put, we have added a GML TimePeriod to each of
> the geoRSS nodes
> along with the spatial representation. Here is an
> example:
>
> <georss:where>
>     <gml:TimePeriod>
>            <gml:begin>2006-06-17T09:55:00Z</gml:begin>
>         <gml:end>2006-06-17T10:30:00Z</gml:end>
>     </gml:TimePeriod>
>     <gml:Point>
>         <gml:pos>37.65356495497155
> -114.5048399056895</gml:pos>
>     </gml:Point>
> </georss:where>
>
> All comments would be appreciated.
>
> Regards,
> brian
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>
>
>
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