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Re: why query languages and RDF data have syntaxes?

From: Dave Reynolds <der@hplb.hpl.hp.com>
Date: Fri, 29 Nov 2002 10:29:34 +0000
Message-ID: <3DE7418E.D7422207@hplb.hpl.hp.com>
To: jeffzhang726@yahoo.com.cn
Cc: "www-rdf-interest@w3.org" <www-rdf-interest@w3.org>

As Andy says the query-by-example approach is particularly useful when you want
to extract a subgraph. We used this approach, to good effect, in a recent
project which involved a lot of queries to remote RDF data sources. All our
retrieval requests were expressed as RDF graphs using bNodes as variables.

As Dan says this can be implemented on top of the richer query languages such as
Squish/RDQL. However, for certain sorts of subgraph extraction it can be rather
more efficient to use a direct implementation. Which is what we used in our
case.

Dave

JeffZhang wrote:
> 
> Dear all,
>     I can not understand why syntaxes of several current rdf query languages are so much different
> with the syntax of RDF data. In my opinion, a query is match a pattern(a subgraph with
> undetermined values) against the universal(the big graph in knowledge base). Why not use
> just a small rdf data set with blank nodes to represent the subgraph?
> I think these query languages have more close relation with sql than with rdf model.
> 
> 
> Best regards,
> 
> 
> JeffZhang
> jeffzhang726@yahoo.com.cn
> 2002-11-29
> 
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Received on Friday, 29 November 2002 05:36:52 GMT

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