W3C home > Mailing lists > Public > public-rdf-dawg@w3.org > April to June 2004

RE: typo correction: Re: Requirement: queries written as RDF (supplants my previous post in this thread)

From: Howard Katz <howardk@fatdog.com>
Date: Fri, 9 Apr 2004 10:34:29 -0700
To: "Eric Prud'hommeaux" <eric@w3.org>
Cc: "Dirk Colaert" <Dirk.Colaert@quadrat.be>, "Rob Shearer" <Rob.Shearer@networkinference.com>, <public-rdf-dawg@w3.org>
Message-ID: <IKEOLCDFPBBPPAHGNKKOCECMEKAA.howardk@fatdog.com>


> Queries are like just about any other piece of intellectual creation,
> someone may want to look for them. An app developer may ask google:
>   What queries look for annotations of documents
>   and give back the body and the creation date?
> I think someone is about a million times (per query instance in the
> envisioned semantics web) more likely to look for published facts than
> published queries.

Sounds like an argument *against* an rdf-based query language, if it's main
rationale is to be able to query queries. Is that what you're saying, Eric?

>
> x I suggested that expressing RDF queries as graphs that can answer
> x those graphs.
>
> I suggested that expressing RDF queries as graphs runs the danger that
> the query graphs can answer those queries
>
>               Patrick dismissed this as bad engineering, but I think
> it's equally likely that creating RDF documents that you don't mean is
> bad practice. For instance, CityBank asks
>   ericP trw:creditRating trw:badRisk ?
> and gets back no matching arcs. If they asked that question within the
> xml element rdf:RDF, the data that they've just sent via whatever means
> to some collection of servers out there on the net has CityBank saying
> that I am a bad risk. Yes, we can draw careful circles around these
> protocols and say "these are NOT expressed as assertions", but I think
> that's a risky practice.

Why is this a danger? If I make a query in XQuery or any other query
language, that in no way is seen as an assertion of what I'm querying; it's
seen for what it is: a question. (And hey, we all love questions! :-) Is
there something inherent in RDF that leads to possible confusion between the
two? It seems a bit odd to me that could happen. But that perception might
be due to my lack of RDF experience...

>
> Another option is to hide the query arc in a reified graph where the
> semantics of some term in the graph stipulate the propositional
> attitude. A consumer of the data will NOT see
>   ericP trw:creditRating trw:badRisk ?
> but instead an encoding of that question that forces them to confront
> at least one term that says "this is a _question_". Architecturally,
> I think this is a safer way to go and provides a less rigid set of
> requirements for the query protocol to insulate itself. In particular,
> I think this is crucial if we adopt Rob's proposed requirement that
> the query lang be useful without the protocol (to tell it not to
> express anything as a truth, in this case).
>
> Third possibility (my favorite), leave this hard work for later. Don't
> bother defining the RDF model representation of a query right now. Use
> a languge that doesn't have any implications in the RDF graph. That
> does not preclude us from using an RDF syntax, we just have to change
> the spelling of the namespace. I'm sure that alarmed 90% of the people
> that read it, but I think it _does_ provide an opportunity for tool
> reuse (with some slight tinkering), and keeps us from pooping where
> we eat by confusing questions with answers.

I'm not alarmed. This seems quite reasonable in fact.

Howard

>
> > > Or do we have a solution without a problem?
> > >
> > > Dirk
> > >
> > > -----Original Message-----
> > > From: Howard Katz [mailto:howardk@fatdog.com]
> > > Sent: mercredi 7 avril 2004 7:08
> > > To: Eric Prud'hommeaux
> > > Cc: Rob Shearer; public-rdf-dawg@w3.org
> > > Subject: RE: Requirement: queries written as RDF
> > >
> > >
> > > 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
> > > unchanged.
> > > > This approach obviously does not take the XML syntax
> requirement very
> > > seriously.
> > > > (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
> > > controversy.
> > >
> > > 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!
> > >
> > > Howard
> > >
> > > > > 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
> > > >
> --
> -eric
>
> office: +81.466.49.1170 W3C, Keio Research Institute at SFC,
>                         Shonan Fujisawa Campus, Keio University,
>                         5322 Endo, Fujisawa, Kanagawa 252-8520
>                         JAPAN
>         +1.617.258.5741 NE43-344, MIT, Cambridge, MA 02144 USA
> cell:   +1.857.222.5741 (does not work in Asia)
>
> (eric@w3.org)
> Feel free to forward this message to any list for any purpose other than
> email address distribution.
>
Received on Friday, 9 April 2004 13:33:45 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 16:15:19 GMT