[ckan-discuss] Calling license URL

John Bywater john.bywater at appropriatesoftware.net
Sat Apr 10 13:51:58 BST 2010

David Read wrote:
> CKAN now gets its licenses from a centralised license server so you
> can get the URLs from here too.
> John, is there some documentation about the license service that we
> can put into the CKAN docs? There's only the initial specs, ticket and
> a brief readme that I know about ( /doc which gets built to
> http://knowledgeforge.net/ckan/doc/ckan/ )

We don't have a "Licenses Service Guide". But there is a Service Level 
Agreement with an accompanying Specification of Service. :-)

Licenses Service - Service Level Agreement:

Licenses Service - Specification of Service:


> In the meantime Lauren, here's what you need: CKAN is setup to access
> the license server by a URL in the ckan config file, in your case
> ca.ckan.net.ini:
> http://licenses.opendefinition.org/2.0/ckan_canada
> So you can convert 'canada-crown' (which is how it's stored in the
> package) to the human readable version 'Canadian Crown Copyright'. And
> all the license properties like openness and URL are given here too.
> It's in JSON format.
> Currently CKAN checks this URL when the vhost is started - usually
> when apache is restarted, so I suggest you do something along these
> lines.

...thinking about this again, I propose presenting the CKAN licenses in 
the CKAN REST API. That would be good service-oriented architecture. It 
would make lots of sense for clients of a CKAN REST API, because they 
wouldn't need to integrate a second interface. It would make lots of 
sense for providers of a CKAN REST API, because they wouldn't need to 
worry about client dependencies when e.g. changing licenses service.

We could present them in the standard way (register + entities), or as a 
single group (like the licenses service), or both?

So Lauren, I also suggest you pull the license entities as a group from 
the license service, as David indicated. Then, at some point, we will 
present the licenses group in the CKAN REST API. After that, you could 
convert your system by simply changing one URL. Then you could forget 
about the licenses service. :-)

Best wishes,


> Hope that helps,
> David
> On 10 April 2010 00:44, Lauren Bacon <lauren at raisedeyebrow.com> wrote:
>> Hello all,
>> I have a possibly stupid question… Hope it won't elicit groans around the
>> world. :)
>> Is there a way to call in the license URL via the CKAN API? We're not seeing
>> it in the data we called in.
>> If it's not currently available via the API, it would be really nice to
>> have; I'd love to put a "more info" link next to the license type on the
>> package info screen.
>> Cheers,
>> Lauren
>> Lauren Bacon | Partner
>> Raised Eyebrow Web Studio, Inc.
>> www.raisedeyebrow.com
>> T. 604.684.2498, ext. 4 | E. lauren at raisedeyebrow.com
>> UFCW Local 1518
>> _______________________________________________
>> ckan-discuss mailing list
>> ckan-discuss at lists.okfn.org
>> http://lists.okfn.org/mailman/listinfo/ckan-discuss

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