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RE: Significant W3C Confusion over Namespace Meaning and Policy

From: John Boyer <JBoyer@PureEdge.com>
Date: Thu, 10 Feb 2005 16:16:45 -0800
Message-ID: <7874BFCCD289A645B5CE3935769F0B5275079F@tigger.pureedge.com>
To: "Elliotte Harold" <elharo@metalab.unc.edu>
Cc: "Robin Berjon" <robin.berjon@expway.fr>, <www-tag@w3.org>

Hi Elliotte,

>John Boyer wrote:

>> It might be the same bag, but it's definitely not
>> the same groceries, and even she would have to 
>> acknowledge the increase in material.

>Point taken, but why are you so convinced the namespace URI identifies 
>the groceries and not the bag? I accept a difference between the bag and 
>the groceries in the bag. It just seems more useful to me to say the URI 
>points to the bag, not the groceries inside it.

The URI is certainly more than just a pointer to a container;
it is intrinsically attached to each name in that container.  
The URI provides the distinguishing component in the full expanded name 
of an element or attribute separates that element or attribute from others 
that have the same local name.  The direct association of the URI and
each name is pervasive, not just in the namespaces rec, but 
also in xpath, infoset, schema and so forth.  To say that 
the URI is meant to be attached to the actual names in every
case except this one is a reach beyond the bounds of reasonable
doubt at what the one sentence in the definition could possibly 
mean.  It implies a hidden inconsistency. Heck even the grammar
error in the definition leads one to believe they're talking about
the names and not the container.

>In your example, I see no fundamental reason why we should consider the 
>namespace URI to refer to the stuff in the bag rather than the bag 
>itself, or vice versa. Pick whichever interpretation is most useful. 
>more than half a decade's experience had pretty well come down on the 
>side that it is very problematic to use namespace URIs as a version 
>control mechanism, so we don't do that.

How does a software module know, for example, which of two
schema documents with which to load the parser if they have
the same target namespaces but describe different sets of
vocabulary?  

How is the meaning of a block of XML protected by a digital 
signature when the meaning can be changed without changing
the serialization?

What happens when an XSLT stops working in a subtle way
because the schema for the namespace changed to make a
required element optional or vice versa? What if the 
problem doesn't get noticed until 10,000 peoples' savings 
disappear on an otherwise sunny afternoon?

Clearly there are also problems with not versioning with
namespaces. Moreover, other than the claim that it is very 
problematic to use namespaces in version control, what's 
your half decade's evidence that it is?

Because I've got over half a decade's experience to the
contrary.  It's no more problematic than writing one's 
vocabulary processor to say match local name plus function 
call to pattern match the namespace URI.  

In fact, the namespace change that occurs for every version
of our XFDL language is the major facilitator in helping us to 
ensure backwards compatibility while evolving our implementations
to add new features. If you have a version 6 form, it will
behave identically when you run it in the version 7 processor.  
So, you can deploy the upgraded processor to get the new 
functionality for new applications without worrying about 
breaking the existing forms applications, which can then be 
upgraded only as the need arises.

And why would this stop the processors in a particular
domain from attempting to process documents of a higher
version (albeit with reduced or erroneous functionality)?

Nope, just can't figure out why some would consider wrapping 
antigen software around this idea when it's so much easier to 
just wrap a function around the check of the namespace URI.

Best regards,
John Boyer, Ph.D.
Senior Product Architect and Research Scientist
PureEdge Solutions Inc.



-----Original Message-----
From: Elliotte Harold [mailto:elharo@metalab.unc.edu]
Sent: Thursday, February 10, 2005 11:03 AM
To: John Boyer
Cc: Robin Berjon; www-tag@w3.org
Subject: Re: Significant W3C Confusion over Namespace Meaning and Policy


John Boyer wrote:

> It might be the same bag, but it's definitely not
> the same groceries, and even she would have to 
> acknowledge the increase in material.

Point taken, but why are you so convinced the namespace URI identifies 
the groceries and not the bag? I accept a difference between the bag and 
the groceries in the bag. It just seems more useful to me to say the URI 
points to the bag, not the groceries inside it.

-- 
Elliotte Rusty Harold  elharo@metalab.unc.edu
XML in a Nutshell 3rd Edition Just Published!
http://www.cafeconleche.org/books/xian3/
http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim
Received on Friday, 11 February 2005 00:17:24 GMT

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