FAqT Service for CKAN Datasets

What is first

• Getting Started
• CKAN - an introduction to using CKAN.
• FAqT Service - how to create one.

What we will cover

This page describes how to use the ckanclient within a FAqT Service to talk to a varying number of CKAN instances.

Let's get to it!

Python

The following services implement how to communicate to a CKAN instance for every resource processed:

• by-ckan-installation.py parses the URI to get the base:

      print 'processing ' + input.subject
      base = input.subject.replace('/$','') 
      api  = base

      ckan = ckanclient.CkanClient(input.subject+'/api')

• lift-ckan.py uses the default ckanclient, but will change it if the dataset is attributed to a CKAN instance:

      ckan = self.ckan
      if len(input.prov_wasAttributedTo) > 0:
         agent = input.prov_wasAttributedTo.first
         print 'CKAN: ' + agent.subject
         if ns.DATAFAQS['CKAN'] in agent.rdf_type:
            ckan = ckanclient.CkanClient(input.prov_wasAttributedTo.first.subject+'/api') 

For example, the following input will lead the FAqT Service to call http://hub.healthdata.gov/api (the /api is appended to the URI of the CKAN):

<http://hub.healthdata.gov/dataset/hospital-compare>
   a datafaqs:CKANDataset;
   rdfs:comment "Omitting datafaqs:ckan_identifier will fall back to parsing the URI.";
   prov:wasAttributedTo <http://hub.healthdata.gov>;
.
<http://hub.healthdata.gov>
   a datafaqs:CKAN;
   rdfs:comment "If the CKANDataset was attributed to a CKAN, ask that CKAN about it.";
.

• faqt.py encapsulates both of these in the method getCKANAPI; it's used like:

   def process(self, input, output):
      print 'processing ' + input.subject
      ckan    = self.getCKANAPI(input)        # returns a ckanclient.CkanClient
      ckan_id = self.getCKANIdentiifer(input) # returns the dataset identifier within CKAN's URI for the dataset.
      try:
         ckan.package_entity_get(ckan_id)
   ...

Java

Java FAqT services can extend edu.rpi.tw.data.ckan.CKANReader.

What is next