WPSClient - A client for assynchronousinteraction with WPS written in Python

Luıs de Sousa, Christian Braun, Chris Eykamp, Ulrich Leopold,Olivier Baume and Rui Martins

Public Research Centre Henri Tudor,Esch-sur-Alzette, Luxembourg.

WPS technologies forIntegrated Assessment Modelling in Urban Areas WorkshopJanuary, 22-24 2014, Belval, Luxembourg

www.tudor.lu

Requirements

A generic application

I A seamless WPS client to be used by a Web Server;

I A generic approach - unawere of databases or clientspecificities;

I Send assynchronous process requests;

I Check process status;

I Retrieve results;I Publish geospatial results to a MapServer instance:

I Vector layers available as WMS and WFS;I Raster layers available as WMS and WCS;I All layers available in EPSG:3857 plus native CRS.

WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, LuxembourgWPSClient - A client for assynchronous interaction with WPS written in Python 2

Design options

I PythonI GDAL/OGR library;I MapScrit library;I Results processing similar to inputs processing in PyWPS;I Performance not crucial.

I Pre-configuarations (not available as application inputs):I MapServer setup;I Aditional CRS;I Fle system locations.

WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, LuxembourgWPSClient - A client for assynchronous interaction with WPS written in Python 3

Difficulties

I Sending requests through HTTP POSTI Required to pass long URLs to WCS and WFS resources;I Thin documentation, few examples available;I Output names must be known in advance.

I MapScriptI No methods available to set up WFS or WCS;I Thinly documented;I Python library hard to read.

WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, LuxembourgWPSClient - A client for assynchronous interaction with WPS written in Python 4

The Map file

A text based generator

I Inelegant code.

I Totally dependent on the Map file syntaxe.

I First version developed in hours.

I Easy to maintain and evolve.

WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, LuxembourgWPSClient - A client for assynchronous interaction with WPS written in Python 5

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, LuxembourgWPSClient - A client for assynchronous interaction with WPS written in Python 6

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, LuxembourgWPSClient - A client for assynchronous interaction with WPS written in Python 7

Future work

I Test with other WPS servers.

I Separate the Map file generator as a sub-module - reusable inother projects.

I Proper XML parsing?

I WPS 2.0 ?

WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, LuxembourgWPSClient - A client for assynchronous interaction with WPS written in Python 8

Thank you

Fork it!

https://github.com/iguess/wpsclient

WPS technologies for Integrated Assessment Modelling in Urban Areas Workshop January, 22-24 2014, Belval, LuxembourgWPSClient - A client for assynchronous interaction with WPS written in Python 9