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Re: RE: why query languages and RDF data have syntaxes?

From: Jeff Zhang <jeffzhang726@yahoo.com.cn>
Date: Fri, 29 Nov 2002 22:10:10 -0800
Message-Id: <200211291405.JAA27020@tux.w3.org>
To: "Seaborne, Andy" <Andy_Seaborne@hplb.hpl.hp.com>
CC: "www-rdf-interest@w3.org" <www-rdf-interest@w3.org>

Dear Seaborne, Andy,
 Dan is right.
 But the point is, as you said, this is a paradigm being liked by programmers.
This fact makes me doubt whether it is suitful for common users. As to Dan's words, the common users are more likely to use more abstract syntaxes building upon the Sql-like query languages, but is it better to insert a programmers' query language  between 
the data and the end-users' query language?
	

======= 2002-11-29 09:30:00 =======

>I think the query languages you have looked at are trying to address the
>problem of getting information out of an RDF model.  They appeal to the
>common SQL paradigm and provide a programming structure that application
>writers are familiar with.  In particular, the result of a query is a set of
>variable bindings, not a gragh (or set of graphs).  Having such a syntax for
>a query is convenient - building queries as an RDF model in a toolkit of
>your choice is a bit tedious.
>
>That said, they do have graph patterns in these languages: e.g.
>
>SELECT *
>WHERE (?x, <ns:property1>, ?z) , (?z, <ns:property2>, ?x)
>
>has a graph pattern in the WHERE clause vaguely emulating N-Triples.
>
>As Dan notes, you can (and people have) use additional decoration of a graph
>to encode the variable name.  You need named variables to (1) get the
>answers out [modulo paradigm] and (2) to encode some graph patterns (shared
>structures).
>
>Where the more explicit graph pattern is interesting is in processing RDF
>into RDF - turning one graph into another.  There is also N3 which has named
>universal variables in the syntax of the language making it clean in writing
>patterns in formulae, differentiating the query variables from the bNodes.
>
>	Andy
>
>-----Original Message-----
>From: JeffZhang [mailto:jeffzhang726@yahoo.com.cn] 
>Sent: 29 November 2002 20:22
>To: www-rdf-interest@w3.org
>Subject: why query languages and RDF data have syntaxes?
>
>
>
>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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Best regards,        

Jeff Zhang
jeffzhang726@yahoo.com.cn
2002-11-29



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Received on Friday, 29 November 2002 09:05:28 GMT

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