W3C home > Mailing lists > Public > www-rdf-interest@w3.org > October 2000

Re: Querying Syntax

From: Ashok Malhotra/Watson/IBM <petsa@us.ibm.com>
Date: Wed, 11 Oct 2000 14:39:50 -0400
To: "Ross Judson" <ross@ManagedObjects.com>
Cc: <www-rdf-interest@w3.org>
Message-ID: <OF47A1345D.BBF80A5C-ON85256975.0066170C@pok.ibm.com>

Its true that XML syntax is verbose and not I'm crazy about it.
The advantage is that it can be easily embedded in an XML
document and can be parsed by an XML parser.

As far as I know, there has been no followup on this.  Neel and
I were planning an implementation but we got distracted.

All the best, Ashok


"Ross Judson" <ross@ManagedObjects.com> on 10/11/2000 02:12:19 PM

To:   <www-rdf-interest@w3.org>
cc:   Ashok Malhotra/Watson/IBM@IBMUS
Subject:  Re: Querying Syntax



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 14:40:27 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:51:44 GMT