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Re: Querying Syntax

From: Ross Judson <ross@ManagedObjects.com>
Date: Wed, 11 Oct 2000 14:12:19 -0400
Message-ID: <00f201c033ae$cd1eae80$221a37ce@mosol.com>
To: <www-rdf-interest@w3.org>
Cc: "Ashok Malhotra/Watson/IBM" <petsa@us.ibm.com>
I've read this before, and I hope you won't mind a little cautious
criticism.  First, XML doesn't seem to make a very good query language by
itself; specialized syntaxes are tighter and, if properly designed, more
readable.  XPath is an example of this.

Here's a quick comparison:

<rdfq:rdfquery>
  <rdfq:From eachResource="http://www.research.ibm.com/people/">
  <rdfq:Select>
    <rdfq:Property name="BelongTo" />
    <rdfq:Select>
      <rdfq:Condition>
        <rdfq:greaterThan>
          <rdfq:Property name="Budget" />
          <rdf:Integer>1000000</rdf:Integer>
        </rdfq:greaterThan>
      </rdfq:Condition>
    </rdfq:Select>
  </rdfq:Select>
 </rdfq:From>
</rdfq:rdfquery>

becomes (further extended to ensure that "BelongTo" is actually a
department):

subjects ((department : startsWith(department,
http://www.research.ibm.com/departments/", "budget", dollars : ge(dollars,
1000000))
THEN
(person : startsWith(person, ""http://www.research.ibm.com/people/),
"BelongTo", department))

I note also that the XML-based syntax is not orthogonal with respect to
querying and navigation amongst all three parts of the triples.

You do have coverage of certain query concepts I have not integrated, like
Quantification and Sorting.

I come at this problem from the perspective of an implementor -- I have an
RDF engine that I want to perform complex queries against.  I needed a
syntax that was conducive to cost optimization.

Your paper was presented during the query language workshop; have there been
other such papers?  Is there any other movement on the RDF query front?

RJ

----- Original Message -----
From: "Ashok Malhotra/Watson/IBM" <petsa@us.ibm.com>
To: "Ross Judson" <ross@ManagedObjects.com>
Cc: <www-rdf-interest@w3.org>
Sent: Wednesday, October 11, 2000 12:28 PM
Subject: Re: Querying Syntax


>
> Neel Sunderesan and I wrote a paper on RDF Query for the XML Query
Workshop
> in December 1998.  Some of you may find it interesting.  You can access it
> at
> http://www.w3.org/TandS/QL/QL98/pp/rdfquery.html
> If you have trouble getting to this I can send you a copy.
>
> All the best, Ashok
Received on Wednesday, 11 October 2000 14:13:25 GMT

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