From GeoRSS

Referencing external geometries

Use cases

1. Often-updated feeds in which entries almost always refer to the same set of semi-static, and possibly complex, locations such as administrative regions. The overall application is improved by not fetching and parsing redundant literal geometry elements.
2. Linking to locations from HTML. Foreign markup isn't welcomed by web browsers, and HTML5 doesn't welcome RDFa, so one must link to locations in other documents.

Possibilities

Note: previous source wasn't coherent, so has been removed for now. Add back in as required. --Sgillies 21:03, 29 April 2009 (UTC)

There's at least two ways to go: use of Atom/HTML links (which better serves the second use case), or use of an optional URI attribute in the georss:where element ala HTML <script> or atom:content (which better serves the first use case).

Atom and HTML links

Would require standardization of a rel type such as "where" (for HTML) or "http://georss.org/relation/where" for Atom:

...
<link
  rel="where"
  type="application/atom+xml;type=entry"
  href="http://pleiades.stoa.org/places/639166.atom#location"
  />
...

And then we'd have to nail down the semantics of "where". Would we want to refer only to georss:where elements within other XML documents using XML ids? Use KML/GML/JSON too?

External source for georss:where

More or less like HTML's <script> tag:

...
<georss:where src="http://pleiades.stoa.org/places/639166.atom#location">
  <!-- empty, filled in by fetching doc from src URI -->
</georss:where>
...

In this case, we'd only accept georss:where markup.