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Re: Significant W3C Confusion over Namespace Meaning and Policy

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Thu, 17 Feb 2005 09:53:31 -0500 (EST)
To: Robin Berjon <robin.berjon@expway.fr>
Cc: Elliotte Harold <elharo@metalab.unc.edu>, www-tag@w3.org
Message-ID: <Pine.LNX.4.61.0502170936300.26332@tribal.metalab.unc.edu>

I completely agree - I think Patrick is also missing the point. First,
Patrick talks quite often of "models" - I'm not sure what exactly he 
means. In the areas I'm familiar with, such as programming language 
semantics or ontologies, models mean a mapping from some syntactic form
to some mathematical object (such as lattice, first-order predicate logic, 
or an abstract state machine ala operational semantics) with 
well-understood properties. So what "model" is being talked about, and
how does it solve the problem of versioning in a both human and 
machine-usable manner? Can you provide me an abstract "model" of a URI,
or URI usage? And if you have a model, how are you going to communicate
about it over the Web? And if you are going to communicate about it over 
the Web, it makes sense one is going to use a URI to do it? And whether
one choses to put the version info in a URI (such as 
www.example.org/xml/2.0/namespace or just www.example.org/xml/namespace
or www.example.org/xml/2.0/namespace/element or 
wwww.example.org/xml/2.0#element?) it seems either way the obvious
place to put *more information* is either in the URI or a namespace 
document. Why not provide standards for both, so applications can get
this *obviously* needed information?

And yes - of course people mix and provide new versions of namespaces - 
that's exactly the problem we're trying to solve. Saying this is a 
*problem*, denigrating a solution (namespace documents), and then not 
providing any positive solution is not solving the problem, it's ignoring 
it. And then saying it's not "licensed in the spec" is fine if it isn't - 
Henry and Roy and such already told us exactly what was in the spec - but 
obviously for some (not all, but some) people are having problems here. So
why not try to think of a solution, and if it proves useful, it may or 
may not be added to the spec, or be provided as an optional spec?

I think a namespace is a perfect place for information about ontologies 
and schemas. A URI is one of the few things a person can own on the Web,
and so it puts the vocabulary\schema\ontology elements in a location. If 
the URI is part of a namespace (as in xmlns is used to identify part of 
the namespace), the value of putting a namespace document with both human
and machine-readeable data in it should be obvious - how else are you 
going to know what an element in the vocabulary\schema\ontology means in 
human readable terms, and where can the RDF describing soemthing be 
gotten from? How else are you going to get information about the model, 
especially if  you are dealing with changing and potentially unknown 
models? The Web is too big for RSS-like namespace change propagation, and
we need decentralized, not Web-wide centralized solutions. Namespace 
documents are decentralized to the owner of the URI of the namespace.

It's obvious RDDL or something like RDDL needs an upgrade to deal with 
versioning. If someone else wants to do the versioning in the URI, that's
fine too, but I think doing it in a namespace standardized RDDL-like thing
is more likely to provide consistency. And then one can mix, change, and 
add things to namespaces - it's just that the namespace document could
reflect that, and different namespaces would resolve to different 
documents. This is so obvious I'm somewhat surprised to have myself 
enumerating the benefits.  And it won't be required - plenty of people 
don't use RDDLs - but those that do should be allowed to. And the positive value of using
standardized ways to talk about versioning and namespaces may provide such 
utility that others will. There's no "MUST" there to "make someone use a 
namespace document" - there is only an option. In the words of RMS, to 
give the users more freedom - but without subtracting from 
interoperability.

 				-harry


  On Thu, 17 Feb 2005, Robin Berjon wrote:

>
> Elliotte Harold wrote:
>> Patrick Stickler wrote:
>>> How is an application to know *which* version of *which* model to
>>> apply in order to interpret the term in question? It can't, because
>>> a given namespace is not tied to a specific version of a specific
>>> model -- insofar as the specifications are concerned 
>> 
>> It's not all about machines. In fact, RDDL was invented primarily because 
>> humans were having trouble with this stuff. Machine processing was an 
>> afterthought.
>
> And to take Elliotte's point further, if namespace documents as currently 
> defined in RDDL and other proposals cannot handle multiple versions (and 
> profiles) of a vocabulary (which is indeed the case) then let's make them 
> handle it. The last time I recall namespace documents being brought up to the 
> TAG the answer was IIRC "after we're done with AWWW v1". This seems like a 
> good requirement to add to the list, in hope that the TAG will tackle it 
> sooner rather than later.
>
>

-- 
 				--harry

 	Harry Halpin
 	Informatics, University of Edinburgh
         http://www.ibiblio.org/hhalpin
Received on Thursday, 17 February 2005 14:53:32 GMT

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