[OSGeo-Standards] Re: [tiling] OGC Tiled WMS Discussion Paper

Christopher Schmidt crschmidt at crschmidt.net
Fri Sep 7 15:00:28 EDT 2007

On Fri, Sep 07, 2007 at 10:47:27AM -0400, Frank Warmerdam wrote:
> Folks,
> I was contacted by Edric Keighan about a discussion paper that was
> recently submitted to OGC (with Cubewerx as the editor) titled:
>    07-057r2 OpenGIS Tiled WMS Discussion Paper

I'm guessing this would be a continuation of OGC 07-057? The editors of
that were not Cubewerx, but from uab.cat, if my records serve. I'd be
interested in seeing either of the two documents, and would ask that  

> I believe it is roughly comparible in goals to this work:
>    http://wiki.osgeo.org/index.php/WMS_Tile_Caching
> I believe Edric is interested in feedback on the paper and support for the
> proposal (for those of us who are OGC members) and perhaps more importantly
> he is interested in implementations of the specification within our projects
> with OpenLayers being the most obvious candidate.

OpenLayers is unlikely to add support for further tiled WMS
specifications through the work of its current set of developers.
Additional layers would need to be created, tested, and supported by
some other person who would accept 'ownership' of the layer type: I've
already avoided including some functionality in OpenLayers simply
because no one was willing to take on the task of supporting it. 

If some person or organization is willing to take on the task of
supporting a layer, then in general, OpenLayers is open to the task of
adding that functionality. However, I'm somewhat hesitant to include
yet-another way of accessing pre-cached WMS information: especially if
it has not taken into account the design goals of the Recommendation we
created at the last FOSS4G, which is described at:


An example of things we explicitly discussed and discarded: 
 * GetTile requests -- we wanted to stick with GetMap, and simply allow
   for matching the map request to a tile when appropriate.
 * Using anything other than the standard GetCapabilities for describing 
   functionality: GetCapabilities allows for vendor extensions, and this
   seemed the right way to pass the information back to the client
 * Starting the tiles at the '0,0' point of the world  (Instead choosing 
   to go for the lower left corner). Note that this is different from
   Google's tiles, but the same as WorldWind's. 
 * Creating any new form of requests -- it's easiest for client
   functionality to simply extend the existing requests rather than
   creating new formats. 

Again, I don't know what's in the document: if someone could tell me
more specifically how to get a copy of it, I could offer a more formal
review from the point of view of an implementor of a tile map server.

Thanks for the heads up, Frank. 

Christopher Schmidt
Web Developer

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