W3C home > Mailing lists > Public > www-rdf-interest@w3.org > January 2005

Re: Exchange of Named RDF Graphs

From: Eric Jain <Eric.Jain@isb-sib.ch>
Date: Wed, 05 Jan 2005 11:59:49 +0100
Message-ID: <41DBC8A5.4030609@isb-sib.ch>
To: Giovanni Tummarello <giovanni@wup.it>
CC: www-rdf-interest@w3.org

Giovanni Tummarello wrote:
> considering statements inside "files which have a name"  seems a naive 
> way to make nothing else than a "bag of reifications" that is a way to 
> assign a URI (the name of the graph) to a bunch of statements. Given 
> that bag of statements can already be done with the existing specs, this 
> is already a reason to drop the idea.. but there is more.

You are right insofar as that in theory everything can be expressed with 
nothing but triples. But in practice many people, including myself, have 
run into problems with this approach, especially when dealing with a lot 
of data.

 > It is clear
> that statements by nature need overlapping bagging.. that is you might 
> want to put certain statements in a certain bag given their order or 
> arrival, their author, their inferred trust level or whatever. With 
> named graphs this .. is just, ops, not possible unless of course you 
> want to copy the statements in different bags. Again with existing 
> reifications + rdf bags this is already possibile..

I wouldn't advocate named graphs as a replacement for reification, but 
as an alternative that is suitable for meta data that applies to 
non-overlapping sets of statements. There may indeed be data sets that 
do not have any such natural groups of statements, but in practice many 
or most do, and those that do will usually need some way to express 
this. Currently the only official way to do so is to use split 
statements into separate files. Unfortunately this does not scale well, 
and doesn't translate well to in-memory or relational storage mechanisms.

> .. and please let us consider past gone the arguments "its too many 
> triples". It should be well understood by now the difference between 
> model theory and practical implementations which are well free to make 
> reifications in the most efficent way they want (e.g. quadruples)

Okay, here is an example. Could you please complete the file found at 
http://www.isb-sib.ch/~ejain/uniprot-rdf/sample.rdf to say that all 
statements have been 'lastReviewed' on '2005-01-05'? Happy reifying! :-)

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Received on Wednesday, 5 January 2005 10:56:12 UTC

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