[PyWPS-dev] Handle complex input of a process within/without a chain in a same way possible?

[Suzana Barreto]

Hi Gunner,

Thanks for getting back to me, yes you have understood my request, I too
tried to use the above example xml template to chain a request but came to
the conclusion that it was failing because the nested <wps:Body> tag was
Geoserver specific - perhaps I was incorrect, if you say that you have a
working chain with RawData.   My understanding is that the server should
seamlessly use the output from one request as input to the next request
without any further coding required because it understands that a nested
request's output is its input parameter, and that is why I thought the xml
request was incorrect.  I too was trying to chain with a ComplexInput that
was the result of a ComplexOutput from a WFS request.  I will have to
revisit it and see what my errors were, perhaps it was not an error in the
xml.  I will keep you posted on my progress, and thanks for the discussion.

Suzana

On Wed, 19 Dec 2018 at 10:32, Gunnar Ströer <gunnar.stroeer at yahoo.de> wrote:

> Hi Suzana,
>
> I agree a process should not know whether it is part of a chain. If you
> ask for a working XML request my example request above works fine for a
> simple chaining. My question aims to the python code behind the request,
> how to handle a chain with PyWPS and without using RawData. Of course it is
> possible to be wrong with my XML. I understand a chained request as a
> nested process of single processes, from inside to outside. The most inner
> request is the first process of your chain (intersection in my case), and
> the most surrounding process ist your last process (buffer in my case).
> I've used following URL for understanding:
>
>
> https://docs.geoserver.org/latest/en/user/services/wps/processes/chaining.html
>
> I hope I understood you correctly.
>
> Best,
> Gunnar
> Am Mittwoch, 19. Dezember 2018, 10:43:54 MEZ hat Suzana Barreto <
> suzana.barreto at envsys.co.uk> Folgendes geschrieben:
>
>
> Hi Gunner,
>
> I have been trying to get chaining to work but have not had any luck yet,
> my understanding is that a process should not know whether it is part of a
> chain.  I would be interested in knowing how you have structured your
> chained request, if you wouldn't mind sharing that information with me.
>
> All the best,
> Suzana
>
> On Mon, 17 Dec 2018 at 13:07, Carsten Ehbrecht <ehbrecht at dkrz.de> wrote:
>
> Hi Gunnar,
>
> I haven’t looked into process chaining, but this question was just raised
> recently:
>
> https://lists.osgeo.org/pipermail/pywps-dev/2018-December/001363.html
>
> Here is in addition a description of how a process chain can be done:
> http://geoprocessing.info/wpsdoc/Concepts#chaining
>
> I’m not sure how your code and your chain works (the gitlab link is not
> public). A comment from my side would be, that your “worker” process should
> not know that it is part of a process chain.
>
> Cheers,
> Carsten
>
> On 12 Dec 2018, at 6:34 pm, gunnar.stroeer at yahoo.de wrote:
>
> Hi Everybody,
>
> I currently develop some processes for a masterthesis using PyWPS v4 as
> implementation. Mostly it works fine for single processes, as well with
> QGIS as client. However I stucked when it comes to chaining.
>
> Normally in single processes I use "in_file =
> request.inputs['in_geom'][0].file" for read in some complex GML geometry.
> In cases I wanna use the same process in a chain the code above doesn't
> work anymore because the input is the same as the output of the prior
> process. Therefore "in_file = request.inputs['in_geom'][0].file"
> additionally gets all the XML code of the prior response - and the process
> crashed.
>
> To handle this I use "import lxml" to parse the response XML looking for
> the "xlink:href" attribute value with the referenced GML output file of the
> first process. It works for the process in a chain, only. Whether the
> process is used in a chain or not I could handle in the process code, like
> a case distinction. Therefor I have to parse XML all the time again and
> again... and it makes me feel that I use PyWPS in a wrong way.
>
> I also could use "RawDataOutput", but this is obviously a bad solution for
> large data inputs/outputs.
>
> Is there any method to handle the described problem without writing too
> much code just to get know whether the process is used in a chain or not?
> Or is there something completely wrong what I'm doing?
>
>
> https://gitlab.com/hadlaskard/integration-of-wps-in-local-sdi/blob/master/processes/proc_buffer.py
>
> Thanks,
> Gunnar
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>
> --
>
>
>
> *Dr Suzana BarretoSoftware AnalystEnvironment Systems*
> Tel: +44 (0) 1970 626688
> www.envsys.co.uk
>
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-- 



*Dr Suzana BarretoSoftware AnalystEnvironment Systems*
Tel: +44 (0) 1970 626688
www.envsys.co.uk

The information contained in this e-mail is intended only for the use of
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