[ckan-dev] CKAN and RDF/SPARQL

Thu May 26 13:01:13 UTC 2011

* [2011-05-26 01:35:29 +0100] David Raznick <kindly at gmail.com> écrit:

] We could start representing extras values as xml instead in the database and
] just decode to python as json like.  We could add this as a configuration
] option at least.  This would be stored procedureable in postgres using
] xpath.

rofl. Yes... I was floating this idea as in, "you could do something
like that if you were insane" though :)

] I personally think we should depreciate json/xml in the extras values fields
] altogether.   It should not be too difficult or troublesome. ckan.net for
] example is always using the extras field as a string anyway (just looked at
] the database), it will not be difficult to sort out this is harvesting code
] which is the only user of it I think.

In general I agree. Apart from saving the original document to
implement a cheap reversible transformation, which the harvesting
machinery does so that a ckan can itself be harvested by a CSW client,
stuffing things like JSON and XML in a blob is a pretty bad idea I
think but I'd not like to start a debate about the relative merits of
different database normalisation strategies.

] Should this solve the issue?

There's another issue with the D2R (which I'm now regretting even
mentioning) which is that because the mapping is from the relational
schema so it can translate SPARQL -> SQL, if you change the relational
schema you have to change the mapping. Since the API is more stable
than the relational schema it is probably less work to use the API.

The tradeoff here is maintenance burden (keeping the mapping in sync)
vs. extra infrastructure (running a triplestore along side). That's
really a judegement call for Ed to make.

Cheers,
-w

-- 
William Waites                <mailto:ww at styx.org>
http://river.styx.org/ww/        <sip:ww at styx.org>
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