Erik Wilde was pondering:
thinking of geofeeds where feed paging does not take you back in time, but increases the search radius. but how to specify paging semantics?
My first feeling is that 'zooming out' is not really a link. Pagination is just a crutch to deal with returning the full set of a single query in meaningful window sizes due to server response, bandwidth, client parsing, and maybe human interface. Zooming out implies actually performing a different search and would be a function of a client interface.
This mechanism is provided by OpenSearch-Geo, which communicates how a client would use a bounding box or polygon search. Therefore a client interface could choose how to zoom out or in and has the capability to query the system this way.
However, I still could imagine more specific uses for such a concept. Erik's original idea is perhaps thinking more about using geography as a way to indicate limiting search set results. This might be done using clustering mechanism, such as k-means, similar to how one might view dense data on a map in clusters, but in search result feeds. The link elements would provide looking into any of these clusters, or zooming in.
Search for 'coffee'
Another way this concept could work more literally would be to utilize a hierarchy, or several hierarchies, that a client may be able to easily snap to in order to query larger or smaller geographic areas. These hierarchies are not apparent in a simple search template and can provide more semantics to indicate the larger area rather than just simply "zoomed out".
For example, using the GeoNames GeoTree or GeoPlanet woeid's, a search result could provide links from the specific bounding box query up to regional or districts that contain this query - as well as perhaps subsets contained within the bounding box.
Search for 'coffee'
title="Search Virginia for 'coffee'" /> href="http://server/search.atom?q=coffee&woeid=12590311"
title="Search Arlington County for 'coffee'" /> href="http://server/search.atom?q=coffee&woeid=12590343"
title="Search Fairfax County for 'coffee'" />
Written on no wifi, sitting in the Detroit airport after a red-eye flight from WhereCamp.