[ckan-dev] CKAN and RDF/SPARQL

[William Waites]

Hallo Ed,

CKAN does not directly support RDF as it uses a relational database to
store the metadata.

There are two strategies you might use to accomplish what you
want. You could work up a mapping with D2R. The advantage of this is
it would make the data directly queriable with SPARQL, the
disadvantage is that the mapping could get quite complicated because
the "extra" fields that are used are just stored as string key-value
pairs, in some cases with the value being a JSON string.

The other way is to have the RDF cache done via the queue. A dataset
gets saved, its JSON representation is sent to the queue and is
processed by some worker processes. This is how the Solr index gets
made, for example, and you would just consider the triplestore as
another kind of index. The advantage is that creating the RDF is
easier, but the disadvantage is that there is still a delay, albeit
much shorter, before the RDF would be available.

Viele gruesse,
-w

* [2011-05-24 14:30:54 -1000] Edzard Höfig <edzard.hoefig at fokus.fraunhofer.de> écrit:

] Hi List,
] 
] we are currently planing to employ CKAN for an open data platform for the city of Berlin, as well as for other cities in the context of the European "Open Cities" project. One of the technical issues that we are still unclear about concerns CKAN's support for RDF and SPARQL. More concretely, we wonder if a single instance of the CKAN software can provide the opportunity to access the meta data of datasets (source, author, etc.) in the RDF format; and furthermore, if it could be configured to provide a SPARQL endpoint to do this.
] 
] We know about the "semantic.ckan.net" website and the CKANRDF extension, but these seem to involve intermediary steps (e.g. polling the data at regular intervals and caching it at an independent location). We would like to be able to directly query a CKAN instance and get results back that are based on the current information stored in that instance (being able to query the "live" data, so to speak). 
] 
] Is anyone else interested in such a system ability? 
] Do you know of any people that are already working on such a feature?
] 
] Cheers,
] Ed
] --------------------------------------------------------------------
] Dr.-Ing. Edzard Höfig
] Senior Research Engineer
] -------
] Fraunhofer FOKUS
] Kaiserin-Augusta-Allee 31
] D-10589 Berlin
] phone: ++49-30-3463-7243 (fax: -8243)
] web: www.fokus.fraunhofer.de/go/motion
] 
] 
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William Waites                <mailto:ww at styx.org>
http://river.styx.org/ww/        <sip:ww at styx.org>
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