[georss] [OpenLayers-Users] GeoRSS and layers

[Mikel Maron]

Your first email included quotes from an OpenLayers user looking to specify an icon within a GeoRSS feed, and that's exactly what I've addressed, never suggesting that MediaRSS was appropriate for anything beyond that. So yes, you are confused.

For an extensible styling solution, I'd prefer to start from SVG.



----- Original Message ----
From: Christopher Schmidt <crschmidt at metacarta.com>
To: Mikel Maron <mikel_maron at yahoo.com>
Cc: georss at lists.eogeo.org; Yves Jacolin <yjacolin at free.fr>
Sent: Monday, January 15, 2007 8:34:32 PM
Subject: Re: [georss] [OpenLayers-Users] GeoRSS and layers

On Mon, Jan 15, 2007 at 08:37:50AM -0800, Mikel Maron wrote:
> For icons, worldKit uses the MediaRSS namespace. http://search.yahoo.com/mrss
> This is the defacto media syndication format, and is used by flickr, among others. 
> For mapping icons, worldkit uses media:thumbnail.
> 
> http://worldkit.org/doc/rss.php#thumb

Perhaps I'm confused, but there are a lot more things to think about
than a thumbnail icon. Describing representation of geographic
information requires describing things like stroke (color, width,
outline), etc. This is what SLD is designed for, and part of what KML 
contains. KML contains additional pieces to also describe the
geographic features, a role which GeoRSS performs on its own, but the
styling/symbolization of geographic features is not something that seems
to fit inside the Yahoo! Media RSS namespace. 

Essentially, so far as I can see it, there are two useful options:
 * Define a subset of SLD, and use that to describe rendering
   information.
 * Define a subset of KML style descriptors, and use that to describe
   rendering information. 

The use of media:thumbnail is fine for single points, but GeoRSS has
support for more than that, and ignoring the other geometry types over
a points-only approach seems like a mistake.

A simple chunk of KML to describe an Icon Style is: 

<Style id="rel1.0">
<IconStyle>
  <Icon>
    <href>http://developers.metacarta.com/img/symbols/mc1.0.png</href>
  </Icon>
</IconStyle>
</Style>

It would probably be possible to include something similar in a GeoRSS
feed:

<rss xmlns:kml="http://earth.google.com/kml/2.0"; xmlns:georss="foo">
<item>
  <georss:point></georss:point>
  <kml:Icon>
    <kml:href>foo</kml:href>
  </kml:Icon>
</item>

At the same time, more complex Styling information can also be included,
when needed, preventing the need for a non-extensible ad-hoc solution.

I don't have enough use cases for GeoRSS that I have a desire to
champion a particular decision here, but I strongly encourage anyone
thinking about this to consider existing standards for geographic data
styling in the discussions.  

Regards,
-- 
Christopher Schmidt
MetaCarta