COST Action TU0902 Meeting: Web Processing Service (WPS) technologies for Integrated Assessment Modelling in Urban Areas

1. WPSClient - A client for assynchronous
interaction with WPS written in Python
Lu´ de Sousa, Christian Braun, Chris Eykamp, Ulrich Leopold,
ıs
Olivier Baume and Rui Martins
Public Research Centre Henri Tudor,
Esch-sur-Alzette, Luxembourg.
WPS technologies for
Integrated Assessment Modelling in Urban Areas Workshop
January, 22-24 2014, Belval, Luxembourg
www.tudor.lu

2. Requirements
A generic application
A seamless WPS client to be used by a Web Server;
A generic approach - unawere of databases or client
specificities;
Send assynchronous process requests;
Check process status;
Retrieve results;
Publish geospatial results to a MapServer instance:
Vector layers available as WMS and WFS;
Raster layers available as WMS and WCS;
All layers available in EPSG:3857 plus native CRS.
WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, Luxembourg
WPSClient - A client for assynchronous interaction with WPS written in Python
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3. Design options
Python
GDAL/OGR library;
MapScrit library;
Results processing similar to inputs processing in PyWPS;
Performance not crucial.
Pre-configuarations (not available as application inputs):
MapServer setup;
Aditional CRS;
Fle system locations.
WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, Luxembourg
WPSClient - A client for assynchronous interaction with WPS written in Python
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4. Difficulties
Sending requests through HTTP POST
Required to pass long URLs to WCS and WFS resources;
Thin documentation, few examples available;
Output names must be known in advance.
MapScript
No methods available to set up WFS or WCS;
Thinly documented;
Python library hard to read.
WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, Luxembourg
WPSClient - A client for assynchronous interaction with WPS written in Python
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5. The Map file
A text based generator
Inelegant code.
Totally dependent on the Map file syntaxe.
First version developed in hours.
Easy to maintain and evolve.
WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, Luxembourg
WPSClient - A client for assynchronous interaction with WPS written in Python
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6. Examples of usage
Starting a process
>>> import WPSClient
>>> myCli = WPSClient.WPSClient()
>>> myCli.init(
... "http://wps.iguess.tudor.lu/cgi-bin/pywps.cgi?",
... "slope_aspect",
... ["dem"],
... ["http://maps.iguess.tudor.lu/cgi-bin/mapserv?map=/srv/mapserv/MapFiles/RO_localOWS_test.map
&SERVICE=WCS&FORMAT=image/img&CRS=EPSG:28992&BBOX=92221,436692,92306,436769
&RESX=0.5&RESY=0.5&VERSION=1.0.0&REQUEST=getCoverage&COVERAGE=ro_dsm"],
... ["slope", "aspect"],
... ["slope_result", "aspect_result"])
>>> url = myCli.sendRequest()
>>> print url
http://wps.iguess.tudor.lu/wpsoutputs/pywps-020cc26a-7f92-11e3-a8a7-005056a52e0d.xml
WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, Luxembourg
WPSClient - A client for assynchronous interaction with WPS written in Python
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7. Examples of usage
Checking process status
>>> myCli = WPSClient.WPSClient()
>>> myCli.initFromURL(url, ["slope", "aspect"], ["slope_result", "aspect_result"])
>>> status = myCli.checkStatus()
>>> print status
True
>>> print myCli.statusMessage
None
Retrieving results
>>> myCli = WPSClient.WPSClient()
>>> myCli.initFromURL(url, ["slope", "aspect"], ["slope_result", "aspect_result"])
>>> status = myCli.checkStatus()
>>> print status
True
>>> myCli.epsg = "3035"
>>> myCli.generateMapFile()
DEBUG:WPSClient:Generated layer slope of type raster.
DEBUG:WPSClient:Generated layer aspect of type raster.
INFO:WPSClient:Wrote map file to disk:
/var/www/tmp/pywps-4d87fa24-7f93-11e3-8b10-005056a52e0d.map
WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, Luxembourg
WPSClient - A client for assynchronous interaction with WPS written in Python
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8. Future work
Test with other WPS servers.
Separate the Map file generator as a sub-module - reusable in
other projects.
Proper XML parsing?
WPS 2.0 ?
WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, Luxembourg
WPSClient - A client for assynchronous interaction with WPS written in Python
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9. Thank you
Fork it!
https://github.com/iguess/wpsclient
WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, Luxembourg
WPSClient - A client for assynchronous interaction with WPS written in Python
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