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RE: Requirement: queries written as RDF

From: Howard Katz <howardk@fatdog.com>
Date: Wed, 7 Apr 2004 22:07:47 -0700
To: "Eric Prud'hommeaux" <eric@w3.org>
Cc: "Rob Shearer" <Rob.Shearer@networkinference.com>, <public-rdf-dawg@w3.org>

I got several responses back from members of the Query wg on the XQueryX
question. I particularly liked this one. I don't know if it'll shed any
light on our own issues, but it's delightfully clear and succinct. The
author prefers to remain anonymous.

In response to a question on why XQueryX:

> (1) An XML-based syntax was considered easier for machines to
> generate and exchange than a human-oriented syntax that would
> require some sophisticated parsing.
> (2) If queries are represented in XML they can be treated as data
> and you can run XQueries over a collection of XQueries.
> (3) Since XML is known to be an answer to all questions, it must be
> an answer to the question "What would be a good format for expressing
> queries over XML data"?

In response to a question on the technical difficulties that arose once the
requirement was formulated:

> Once the requirement for an XML query syntax was adopted,
> arguments immediately broke out over the level of detail at which a query
> should be broken down into XML elements. The working group finally settled
> on two separate approaches that represent extreme points on the spectrum:
> (a) The whole query is wrapped in a <query> element, and otherwise
> This approach obviously does not take the XML syntax requirement very
> (b) The query is parsed, and each and every node in the parse tree
(including individual
> operators, function calls, steps in path expressions, etc.) is represented
by its own
> element, thus making the query incredibly verbose. This format is
obviously useless to humans.

> At various times and places, people have attempted to define some
intermediate point
> between these two extremes. These attempts have always ended in rancor and

Finally, in a follow-up clarification:

> I believe that the editor of the XQueryX specification is currently
pursuing both approaches
> (a) minimal expansion and (b) maximal expansion. Both will be defined as
valid forms of
> XQueryX.

Just to close on a personal note, I've always felt that XML is the answer to
all questions. I'm now coming to feel increasingly that RDF is even more so!


> > On Sun, Apr 04, 2004 at 09:23:14AM -0700, Howard Katz wrote:
>    [snip ...]
> > > I certainly agree with the sentiments of the second, "human readable"
> > > requirement. Interestingly enough, the third, "XML" requirement
> > has been the
> > > one that's caused the group the most difficulty to my
> > knowledge, and at the
> > > moment conformance with this requirement has been downgraded to
> > optional. I
> > > don't know what the major issues have been, but it might be
> > interesting to
> > > know, if only for the sake of curiosity.
> >
> > Can we go beyond the meta-lesson of "that may be hard. it's been hard
> > in XQuery" to some of the particular problems that requirement caused
> > the XQuery WG? Also, was this requirement born of some compelling use
> > cases, or a general notion that it's good practice to express anything
> > in XML?
> I wasn't trying to impart a particular lesson. My intention, not knowing
> what DAWG members know or don't know about it, was simply to
> provide data on
> the experience of the Query wg in the event that might prove useful to the
> group. In response to your questions, I've asked several members of the wg
> about their XQueryX experience. If they see fit to pass that on
> to me, I'll
> be happy to share it with the group.
> Howard
Received on Thursday, 8 April 2004 01:06:47 UTC

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