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<div class="moz-cite-prefix">Le 03/12/2012 14:05, Martin Dobias a
écrit :<br>
</div>
<blockquote
cite="mid:CAC2XbFfjh04uKAUStp3=0pK_6RWoz=2sqK6YLzku=-ufnmpWwA@mail.gmail.com"
type="cite">Hi Rene-Luc<br>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Mon, Dec 3, 2012 at 10:01 AM,
rldhont <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:rldhont@gmail.com" target="_blank">rldhont@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">With the
QGIS Expression you just have to know how to write an
expression to create a new Process. It's not coding.<br>
For example the Buffer Process can be described like this :<br>
buffer("geometry","distance")<br>
You want to create a Process which retrun the buffer without
the geometry :<br>
difference(buffer("geometry","distance"),"geometry")<br>
And we can define a Process which return the result of a
QGIS Expression as the Process parameter.<br>
</blockquote>
<div><br>
</div>
<div>Thanks for sharing your thoughts about your
implementation.</div>
<div><br>
</div>
<div>
I would like to express my concerns that using QgsExpression
may be a dead end for a generic WPS servers. Expressions are
meant to deal with individual features of a vector layer.
You're right that it's possible to define your own functions
and chain them to create processes, but this is very
limited. For example it's not possible for a process to
return more results and it's not possible to use one result
more than once. Just like raster calculator has its own
expression engine, also the processing service should use a
way of describing algorithms that suits best its needs - and
in our case that's python+SEXTANTE.</div>
<div><br>
</div>
<div>Therefore I strongly recommend using SEXTANTE for the WPS
server backend. I believe that would be less work than
trying to hack QgsExpression to use it for processing. You
would just need to parse WPS query, generate a Python script
that would run SEXTANTE analysis and then create WPS reply.
It's probably not desirable to run the processing directly
within the server process (thread), so this would be a
better solution either way.</div>
</div>
</div>
</blockquote>
<br>
Hi Martin,<br>
<br>
My idea was to have a simple WPS server based on QGIS-Server, very
simple for simple vector case, and I thought it's a good idea. I
only need to validate geometry, constructing simple buffer or
intersection.<br>
<br>
For big processing, I think SEXTANTE is better suitable, but for a
WPS serveur, SEXTANTE didn't need QGIS. We can construct a WPS
Server based on pySextante with pyWPS.<br>
<br>
I don't really want to hack QgsExpression, just accesses to very
simple processing, I'll just it. For SEXTANTE, It will be better to
work on someting based on pyWPS.<br>
<br>
René-Luc<br>
<br>
<br>
<blockquote
cite="mid:CAC2XbFfjh04uKAUStp3=0pK_6RWoz=2sqK6YLzku=-ufnmpWwA@mail.gmail.com"
type="cite">
<div class="gmail_extra">
<div class="gmail_quote">
<div> </div>
<div>Regards</div>
<div>Martin</div>
</div>
</div>
</blockquote>
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