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

Re: Summary of the QName to URI Mapping Problem

From: Aaron Swartz <aswartz@upclink.com>
Date: Thu, 16 Aug 2001 12:44:09 -0400
Message-Id: <200108162034.f7GKYEf20760@theinfo.org>
To: Patrick.Stickler@nokia.com
Cc: sean@mysterylights.com, RDF-Interest <www-rdf-interest@w3.org>
On Thursday, August 16, 2001, at 07:15  AM, 
Patrick.Stickler@nokia.com wrote:

>>> I.e. if 'ns1:' = "urn:x:abc" and 'ns2:' = "urn:x:abcd"
>>>      then both 'ns1:defg' and 'ns2:efg' are mapped to
>>>      the same URI "urn:x:abcdefg"! Yet these are clearly
>>>      separate resources per their disjunct QName identities
>> Really? Says who?
> Uhmmmm... the XML Namespace spec. No?

Nope. It doesn't say anything about the meaning/identities of QNames.

>> RDF defines a QName->URI mapping for RDF
>> documents. RDF documents must follow this mapping.
> *Documents* must follow that mapping? Don't you mean systems? And
> what about RDF content that will be derived on-the-fly from other
> representations or other serializations where the content producers
> don't even know their stuff is being groked as RDF and thus don't
> choose the namespace URIs "carefully"? (see below re RDBMS's)

Then why is it being written as RDF? I don't follow this 
argument at all.

>> QNames mean nothing special in RDF. Look at
>> N3 -- foo:bar can be replaced with <http://foo#bar> (or whatever
>> the foo prefix is defined as) with no loss in meaning.
> Sure, presuming that (a) the namespace ends in a non-name character
> which preserves the namespace/name boundary upon concatenation, and

Why is this necessary?

> (b) that the namespace was custom-tailored to the RDF interpretation
> of, or custom treatment of, QNames.

Well, you'd assume this would be true if someone was using this 
in an RDF document.

> Are you telling me that we cannot expect folks to want to re-use
> existing XML content models which are compatible with the RDF
> serialization structure as property elements and which may have
> namespaces based on URIs for which the '#' at the end hack doesn't
> work?

Umm... I don't expect folks to reuse XML content which is not 
valid RDF. That is true even if the bit that makes it invalid is 
the URI. Yes, it's nice to reuse XML content, but really, has 
this every been a real-world issue? Most XML content models use 
name URI-refs that can easily be concatenated. (Almost all, I'd 

> Are you telling me that in order for QNames to work in RDF that
> their namespace URIs have to be "special" URIs?


> Sorry, I just don't see that flying on a global scale. If RDF is
> going to "adopt" URIs and QNames, then it must do so in a generic
> and non-discriminatory fashion.

We're not "adopting" them, we're inviting them over for a play date.

> What if those don't fit the special criteria
> seemingly required by RDF? Do we have to hack up mapping filters
> to "fix" all the namespaces? Do all the namespaces have to be changed?
> I can hear the RDBMS owners laughing (or groaning) already now...

Well, the chances that the resulting XML fits the RDF 
serialization doesn't seem all that great to me anyway...

> Please have a look at my posting 'A proposed solution to the RDF
> syntactic/semantic mapping problem (long)' for examples of the kinds
> of issues I am dealing with and the kind of solution I feel RDF should
> provide. I'd also be happy to email it to you.

I'd appreciate that, I don't seem to have it in my local archive.

[ "Aaron Swartz" ; <mailto:me@aaronsw.com> ; <http://www.aaronsw.com/> ]
Received on Thursday, 16 August 2001 16:32:41 UTC

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