W3C home > Mailing lists > Public > www-rdf-interest@w3.org > November 2003

Re: Semantic Web Phase 2 Activity - Protocol - Query Language

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Tue, 11 Nov 2003 14:00:01 +0200
To: <leo@gnowsis.com>, <www-rdf-interest@w3.org>
Message-ID: <BBD69BE1.4C66%patrick.stickler@nokia.com>

On 2003-11-11 12:27, "ext Leo Sauermann" <leo@gnowsis.com> wrote:

> 
> In the last time I stumbled across the "Semantic Web Phase 2 Activity"
> more often and expect that some people involved read this.
> 
> In my writing code, I clearly miss some things that would make life
> easier:
> so I think that they should be included in Phase2.

We clearly share similar concerns/interests.

> TimBl wrote that you need three things to build a WWW:
> HTTP, HTML, URL
> We clearly miss the HTTP part so at first i ask for :
> 
> 
> A PROTOCOL
> ==========
> uriqa, Joseki, Sesame, they all have protocol.
> 
> We are missing a protocol, so do something about it.
> 
> important:
> - distributed approach, how to identify the server when querying about a
> given resource.
> (see my comments about this in
> http://lists.w3.org/Archives/Public/www-rdf-interest/2003Oct/0155.html)
> 
> - queries over the protocol with query language

I'm not sure if full querying must be bound to the core protocol,
as the core protocol should be as ubuiquitous as possible and having
too great an implementational burden would hamper that.

I've drawn the line between a minimal protocol for "bootstrapping" the
SW (i.e. URIQA) via which one can discover other supported protocols,
APIs, services, etc. which a given server may support. E.g. if one
executes the request

MGET http://sw.nokia.com HTTP/1.1

one gets back a description of the Nokia Semantic Web Server which
indicates various services available, including a URIQA service for
arbitrary URI queries as well as an RDFQ service for advanced
queries. I.e.

<?xml version="1.0"?>
<rdf:RDF 
   xmlns:swarch="http://sw.nokia.com/SWArch-1/"
   xmlns:uriqa="http://sw.nokia.com/URIQA-1/"
   xmlns:webarch="http://sw.nokia.com/WebArch-1/"
   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
   xmlns:owl="http://www.w3.org/2002/07/owl#">
    <rdf:Description rdf:about="http://sw.nokia.com">
        <rdf:type rdf:resource="http://sw.nokia.com/URIQA-1/Server"/>
        <uriqa:service rdf:resource="http://sw.nokia.com/uriqa"/>
        <swarch:service rdf:resource="http://sw.nokia.com/rdfq"/>
        <webarch:service rdf:resource="http://sw.nokia.com/id"/>
    </rdf:Description>
</rdf:RDF>

Standardization of other, more involved protocols/APIs for advanced
query, distributed knowledge management, rules, etc. need not overburden
the deployment of that essential bootstrapping functionality.

> and some kind of
> "Concise bounded description"

Most definitely.

> 
> 
> A Query Language
> ================
> RDQL, RQL ....
> 
> all nice but a common lanugage should include :
> - OUTER JOIN Queries, (optional matches)
> - giving a "template" for a subgraph to be retrieved, f.e.
> "give me triples that do: (?x rdf:type foaf:Person), (?x * *)"
> 
> (these two things are in some projects, but not in all etc....)

I think that RDFQ [1] includes both of the above, but would be very keen
to learn if it didn't.

The boolean logic of an RDFQ query input graph is

rdf:RDF
{
   rdfq:Query
   {
      ...
   }
OR
   rdfq:Query
   {
      ...
   }
OR
   rdfq:Query
   {
      rdfq:Target
      {
         ...
      }
   OR
      rdfq:Target
      {
         ...
      }
   OR
      rdfq:Target
      {
         PROPERTY VALUE
      AND
         PROPERTY VALUE
      AND
         PROPERTY rdfq:Value
         {
            CONSTRAINT=true
         AND
            CONSTRAINT=true
         AND
            ...
         }
      }
   }
}

Optional matches could also be defined in terms of a best-match
algorithm, where targets are ranked according to the degree to which
the template matches their description (by some formula).

I.e., RDFQ provides the means to specify one's ideal target, whether
or not matched resources satisfy that ideal and
whether such less-than-ideal resources are described in the results
is not necessarily dependent on the query language.

Though, if this is a strongly desired feature, it would be straightforward
to define a subclass of rdfq:Value, i.e. rdfq:OptionalValue, or some similar
machinery to provide for this.

> 
> URI Crisis guide
> ================
> Personally, I think that
> "http://www.amazon.com/exec/obidos/ASIN/0679600108/qid=1027958807/sr=2-3
> /ref=sr_2_3/103-4363499-9407855" is a webpage that offers a book for
> sale and that means
> 
> <http://www.amazon.com/exec/obidos/ASIN/0679600108/qid=1027958807/sr=2-3
> /ref=sr_2_3/103-4363499-9407855> <sale:offers>
> <http://www.isbn.org/US/0679600108>
> 
> and sadly, the www.isbn.org guys don't offer a search for books on their
> site and so we can't extract a url for  0679600108 from their site, but
> this ought to change !
> 
> I think that <http://www.isbn.org/US/0679600108> is a global identifier
> for the book and it should be used to represent the concept of the book
> and used extensively in databases of Bookstores and semantic text
> rezensions all over the world.

I agree. Though such use could only ever be voluntary.

> But thats what I think and the W3C ought to state what we should do now
> about it and create some document where this is settled.

I think the most that could/should be done is to provide the means for
folks to say what their URIs denote and provide consistent, standardized
access to descriptions of those resources. I don't think we can tell
folks that they must create certain URIs or what URI scheme they must
use, etc. -- though promotion of certain "best practices" is certainly
something the W3C could (and of course is working to) provide.

> I think this problem can be best settled by philosophers, librarians and
> SemWeb people in concert.

Now *that* sounds like a fun party ;-)

Cheers,

Patrick

[1] http://sw.nokia.com/rdfq/RDFQ.html


> 
> 
> Greetings
> 
> Leo Sauermann
> www.gnowsis.com
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Dear God, 
> For christmas 2003 I wish that you solve these things.
> :-)
> 
> 
Received on Tuesday, 11 November 2003 07:02:18 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:52:03 GMT