W3C home > Mailing lists > Public > www-rdf-interest@w3.org > June 2001

Re: What to do about namespace derived URI refs... (long)

From: Sean B. Palmer <sean@mysterylights.com>
Date: Fri, 8 Jun 2001 15:13:59 +0100
Message-ID: <022301c0f026$2066b7c0$d7dd93c3@z5n9x1>
To: <Patrick.Stickler@nokia.com>, <seth@robustai.net>, <www-rdf-interest@w3.org>
Cc: <Ora.Lassila@nokia.com>
> The crux of the problem is not whether URLs and URL refs
> can be made to work as names -- obviously they can -- but
> whether those names are sufficiently persistent and universal
> to be used in all contexts and for all methods of interchange,
> particularly and especially in the case of namespaces.

Yep, that's true, but not only that, it's the fact that many people
don't have a persistent address in which to create URI. And the SW is
meant to be universal? Well it's not if you can't afford to make a
namespace. Sure, you can use an MID or something, but I have a feeling
that many people wouldn't even have a clue what that is. Tags and so
forth can use email addresses, and have a date algorithm that somebody
on a Western date time can work out in their heads. Pretty neat.

But that doesn't mean that URI Refernces with an HTTP URL base are
broken - as you yourself admit later on in the message...

> >    { :r1 a http:Reply; :from :r2; :content :bytes.
> >       :bytes :xmlParseAs :dom;
> >      :dom [ :xpath "html/head/title" ] :t }
> >    log:implies { :r xhtml:title :t }.
> >

Oops, "s/:dom;/:dom ."

> [...]
> Sorry, I don't yet grok the new (unofficial) syntax. Can you give
> in the XML syntax? Thanks.

Well, I advise that you learn Notation3, because it's a laugh:-


But here it is in XML RDF anyway:-

<rdf:RDF xmlns:http="http#"
        <rdf:is rdf:parseType="Quote">
                <xpath xmlns="#">html/head/title</xpath>
            <rdf:Description rdf:about="#bytes">
                <xmlParseAs xmlns="#"
            <rdf:Description rdf:about="#dom">
                <_g1 xmlns="#"
            <rdf:Description rdf:about="#r1">
                <rdf:type rdf:resource="file:http#Reply"/>
                <content xmlns="#"
                <from xmlns="#"
        <log:implies rdf:parseType="Quote">
            <rdf:Description rdf:about="#r">
                <xhtml:title xmlns="http://www.w3.org/xhtml/"

Just a tad longer (hmm... CWM is giving out quite a few bugs on this

> Well, as RDF does not dereference its URI refs, but only
> uses them as unique strings -- trusting the definition of and
> mechanisms relating to URIs to ensure that uniqueness, then
> SW apps need not grok any kind of URI whatsoever, eh?

CWM dereferences certain URIs if you ask it to now.

   :x log:resolvesTo :y .

It'll try to resolve :x, parse it, and store it in :y.

> Just because there is e.g. a rdfs:seeAlso or rdfs:isDefinedBy
> property that points to a URI doesn't mean that any SW
> application has to either be able to dereference that URI or
> understand its content (presuming its a URL).

It also doesn't stop one from doing so.

> As I mentioned above, so long as all of your rdf:about
> strings are unique in a given context, regardless of what
> they are, then there are no problems.

So then you admit there is no problem here with the URI references
that these applications use? Great.

> E.g. precisely how does one relate xml:lang="en" to the
> ISO 639 language "English"? Or the value in
> <format>text/xml</format> to the IETF RFC 2045
> "text/xml"?

You write that into your software. It would be nice if machines could
bootstrap this stuff in, I admit, but at some level in the Semantic
Web, you get prose definitions of primitives.

> [...] there are no explicit and reliable mechanisms in XML
> Schema (or DTDs) for defining user-palatable serializations
> of metadata which would be parsed by an RDF parser [...]


Kindest Regards,
Sean B. Palmer
@prefix : <http://webns.net/roughterms/> .
:Sean :hasHomepage <http://purl.org/net/sbp/> .
Received on Friday, 8 June 2001 10:18:58 UTC

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