[mapserver-dev] INSPIRE Category Layer (may affect 6.0 release)

[Martin Kofahl]

Hi all,

if MapServer 6.0 shall support Inspire View Services, MapServer should 
be able to serve named wms group layers as discussed elsewhere on this 
list. Currently the wms_layer_group setting does not provide named group 
layers. (And because of the nesting depth we cannot use the group keyword.)

Following ticket http://trac.osgeo.org/mapserver/ticket/1632 I propose 
that the wms_layer_group keyword may reference a real map layer. This 
change would not interfere present use of the wms_layer_group setting. 
When wms_layer_group is evaluated, MapServer checks if a map layer with 
such name is available. In this case msDumpLayer() will write the group 
layer with all its capabilities and otherwise write only the title 
(present behavior).


Compared to the use of the group keyword this technique requires 
thoughtful map file configuration, because the a layer is not 
necessarily the sum of all sub layers. This may also be an interesting 
feature for some use cases. For the drawing process there are two 
possible map file configurations:


a) Fully configured map layers shown as group in the capabilities. They 
shall contain all data which the nested layers show. (Or even not if one 
may present a simplified group layer in case of huge amount of nested 
layers/data.)


b) Dummy group and nested layers. Drawing process is done by hidden 
layers using the REQUIRES keyword, e.g. REQUIRES ([group] || [nested_layer])



Currently, the patch attached to #1632 dos not filter map-layers used as 
group-layers beforehand. Thus group layers are currently dumped twice if 
it's not hidden using #1952.


Martin

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