[ZOO-Discuss] ZOO OnGoing Project : The Laurent Jégou Blog story

[Gérald Fenoy]

Hi ZOO Tribe member,
I have a story to share with you. 


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Today, in the cold of France, *somebody* called me on phone and tell me that Lourent Jégou wrote an article on his blog [1] about using R with pyWPS.
Laurent also mentioned that he did this choice, using pyWPS, cause ZOO Kernel is still unavailable (I use ZOO Kernel here, even if he spoke about "Zoo", in fact he means ZOO Kernel here). Oups, sorry for this point.
So, *somebody* send me the link [2], unfortunately I wasn't in front of my computer so unable to read anything :). I asked him if the python code quoted in the article was available or not. As, he answered me it was, I told him that I call him back to tell him when the process was modified to be used from the ZOO Kernel.

So I gone back on my computer and check this web page, fethcing the python code then copying the logic only included in the python file from the article  (no metadata, as metadata and logic is separated in ZOO Kernel).

Here "the logic code" I talk about was pointed in the full ServiceProvider, providing only one service called discretise :

import rpy2.robjects as robjects
import sys

def discretise(main,inputs,outputs):
       # the following lines are need only because of 
       # strange issue specific to R displaying msg :
       # Loading required package: class
       try:
               sys.stdout.close()
       except:
               pass
       # The logic code
       robjects.r('library(e1071)')
       robjects.r('library(classInt)')
       robjects.r('library(XML)')
       robjects.r('data(jenks71)')
       robjects.r('doc = xmlRoot(xmlTreeParse("%s"))' % inputs['donnees']['value'])
       xsa = robjects.r.xmlSApply
       jenksData = robjects.r('xmlSApply(doc, function(x) as.numeric(xmlSApply(x, xmlValue)))')
       ci = robjects.r.classIntervals
       tmp=int(inputs['nbClasses']['value'])
       out = str(ci(jenksData, n = tmp, style = inputs['methode']['value']))
       outputs["Result"]={"value": out,"dataType":"string"}
       return 3


Then I copied the hellof.zcfg metadata file (the ZOO Configuration File for the sample Fortran ServiceProvider) into a new one called discretise.zcfg. I tested ... it and it works :)
In fact it shuldn't work but I know that ZOO Kernel is really permissive when passing arguments to ServiceProvider function.... This explains why the hellof.zcfg file was enough to run the process... Nevertheless, in some sens, that let devs make their tests on their new service provider before putting them publicly available all over the web..
So I correct a bit the ZOO Configuration file to get a realistic DescribeProcess.

Finally, few minutes was requested to turn a simple pyWPS service into a service from a ServiceProvider Python Based to be run from the ZOO Kernel. I called back *somebody* :)

I know it's not such an interesting example, but it let me think that the ZOO Kernel is a good tool to easily use an already existing code as a WPS service, even if it was not (a service) at the begining. Please, correct me if I'm wrong.

So, even if here we duplicated a WPS service to create a new one, comparison between two solutions can be easily made for everyone reading this story. It contains also a view about what have to be done to integrate your own  (Python here) code as a ServiceProvider providing WPS services through ZOO Kernel.

Separation between metadata and services as a staring point, multi-language support in an embedded way to take control over service to provide.

Parameters storeExecuteResponse was supported since the begining of ZOO Kernel development (cf. hello worlds from various embedded languages [3], [4] and [5]). It let users decide if they want to store the ExecuteResponse (on the current demonstration server we remove files quickly) to let him fetch/poll the statusLocation provided in the execute answer from its client application to show status of execution and be informed when the process was ended. It can be useful for applcication using a cache or something.

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[1] http://www.geotests.net/blog/
[2] http://www.geotests.net/blog/article/mise-en-place-d-un-webservice-de-discretisation-en-utilisant-pywps-et-r
[3] http://demo.zoo-project.org/zoo/?request=Execute&service=WPS&version=1.0.0&Identifier=hellof&DataInputs=S=Your%20Name%20Here@datatype=string&storeExecuteResponse=true
[4] http://demo.zoo-project.org/zoo/?request=Execute&service=WPS&version=1.0.0&Identifier=HelloWorldJava&DataInputs=S=Your%20Name%20Here@datatype=string&storeExecuteResponse=true
[5] http://demo.zoo-project.org/zoo/?request=Execute&service=WPS&version=1.0.0&Identifier=HelloPHP&DataInputs=S=Your%20Name%20Here@datatype=string&storeExecuteResponse=true

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*somebody* was abviously Nick !

Hope to hear from you ZOO Tribe members,


Djay
Just a ZOO Monkey
gerald.fenoy at geolabs.fr

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