[WMS Server] Need clarification in docs for layers with STATUS DEFAULT

[dmorissette]

Frank W. wrote:
--------

Daniel and others,

I have been experimenting a bit with the Gaia WMS viewer
(http://www.nukegold.com/downloads.htm) a bit against MapServer, and
found something that surprised me.

It seems that a layer with STATUS DEFAULT will be returned in a GetMap
request against MapServer regardless of whether the layer is in the
layers list or not.  Is this the expected behaviour?

I have a WMS server (from CVS) servering 3 layers, all of which have
STATUS DEFAULT.  Even if I ask for just one of them, it would appear I
get all 3.

I would have hoped MapServer would have:
 o returned only the requested layers if there is a LAYERS= parameter
   in the WMS GetMap request.
 o Returned only STATUS DEFAULT layers if there was no LAYERS= parameter
   in the WMS GetMap request.

If things are behaving as intended, then I think the WMS Server HOWTO
should mention this gotcha.

[dmorissette]

This is the expected behavior, which is in line with the behavior of the
original mapserv CGI in which layers with status default cannot be turned off.

We should update the docs.

[dmorissette]

Actually, the WMS server HOWTO should discourage the use of STATUS default in
WMS servers "unless you know what you're doing".

[fwarmerdam]

Agreed Daniel, although it is unfortunate that this conflicts with the 
non-WMS advice I give for layers which is that folks should use STATUS DEFAULT
unless they know what they are doing. 

[dmorissette]

Well, using STATUS DEFAULT for the CGI is not a good thing either since you
cannot turn those layers off using the normal mechanisms... so you may have to
change the advice you give to be:  "Set layers to STATUS DEFAULT while debugging
a problem, but set them back to ON/OFF in normal use."

I'll CC Steve to get his opinion on this.

[fwarmerdam]

Good point ... just goes to show how dangerous it can be having someone 
with little mapserver application level experience giving advice!

[sdlime]

My opinion would be to leave well enough alone, don't change any behavior. I don't think anyone was 
though. I think a thorough explanation of what ON/OFF/DEFAULT settings in the mapfile mean in 
various settings would be very useful for novice and experts alike. Something like:

                                           ON                         OFF                          DFAULT
CGI       
MapScript
WMS
WFS/WCS
Command line utils

Language in each cell could explain the effect in each case. For example, fof CGI/ON it might say NO 
EFFECT and for MapScript/ON it might say HONORED.

I dunno, just an idea. It would be great to unify behavior but I'm afraid that will be very difficult at this 
juncture.

Steve

[jmckenna@…]

moving to documentation Component

[jmckenna@…]

i added a note in the wms server doc about the status default behaviour.  also
added a few points in the mapfile-reference under layer STATUS.  

not the fancy thing Steve suggested, but it's a start.  If anyone is not
satisfied please reopen.