[mapserver-dev] MS RFC 68: Support for combining features from multiple layers (Call for discussion)

[Frank Warmerdam]

On 11-02-10 05:02 PM, Tamas Szekeres wrote:
> Hi Devs,
>
> In reference to the feature request from WhereGroup
> <http://www.wheregroup.com/en/welcome> we did some refinement in the
> specification and I've created MS-RFC-68
> (http://trac.osgeo.org/mapserver/browser/trunk/docs/en/development/rfc/ms-rfc-68.txt)
> which contains a reasonable implementation to this option without requiring
> significant modifications in the MapServer codebase and the current processing
> chain. With regards to the timing, I already have some working code in place
> which could be finished by the time of the feature freeze of MapServer 6.0 we
> are targeting now (feb. 28).
>
> Waiting for your comments and suggestions...

Tamas,

I have only made a cursory review of the RFC and can't really spend the time
to give good feedback.  However, overall I find the proposal intimidating.
A few more specific concerns:

  1) I would be more comfortable if you didn't need to modify the behavior
     of the source layers.  Why not have the aggregate layer have a list of
     the source layers, insteading of marking source layers with the
     target layer that will consume them?

  2) Are you planning to use the functions in maptree.c as a generic quad
     tree or are you hoping to take advantage of .qix files for shapefile
     sources?

  3) Are you planning to do clustering for dissimilar features from
     different sources?  At the core I don't understand why the clustering
     needs to have multiple source layers.  It seems like combining
     features from multiple layers and clustering features should be
     distinct operations.

If the actual effect on other layer implementations is very minor, and all
the complexity is in mapcluster.c and used only when the new feature is
active then I suppose it doesn't matter that much.

I will say that the clustering ideas seems very powerful and useful.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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