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RE: Varying the attlist for an element depending on the element's parent

• From: Andrew Layman <andrewl@m...>
• To: 'james anderson' <James.Anderson@m...>
• Date: Thu, 10 Dec 1998 11:46:34 -0800

Thank you for you mail.

What I was trying to make clear--and perhaps failed to make clear--is that
the namespaces proposal is fairly limited in its scope.  As you say, it does
not preclude potential mechanisms that might be invented in the future for
making the legal syntax of elements dependent on their context, but at the
same time, it certainly takes no obvious steps in that direction.  As one of
the editors of the proposal, I can assure you that such a mechanism was
never in my mind as I worked on the proposal, and if it had been, I would
not have seen it as an aspect of namespaces per se but rather of schemas.

The namespace proposal serves to permit a simple, standardized mapping from
an element or qualified attribute name to a single URI.  That is it.  It
really says nothing about the processing of the URIs.

I'm deliberately not commenting on the desirability of having attlists vary
depending on context, because that is an orthagonal issue to namespaces.
However, I would recommend a general caution against inferring semantics
based on namespaces.  It is generally much safer to allow the namespaces
mechanism to simply confer universal identity to elements and attributes,
with other mechanisms (such as schemas or architectures) then defining
semantics.

-----Original Message-----
From: james anderson [mailto:James.Anderson@m...]
Sent: Thursday, December 10, 1998 6:01 AM
To: Andrew Layman
Cc: XML Dev
Subject: Re: Varying the attlist for an element depending on the
element's parent


While the namespace proposal as it stands does not describe "facilities for
defining syntax or semantics", it is by no means silent on them.
My note was so full of subjunctives that I trust no one understood it to
suggest that the namespace proposal prescribed such a mechanism.
It pointed out only that the proposal, as it stands, does not preclude such
a
mechanism. An alternative wording in the noted paragraph could have done so.
It is a rather severe understatement to equate the passage with "silence".

Andrew Layman wrote:
> 
> The paragraph quoted below beginning "Each Type..." is intended only to
> describe scoping of attribute names matching the scoping expressed in DTDs
> today.  That is, it simply says that the (unqualified) attlist for
distinct
> elements types is distinct; that the unqualified attribute types of
distinct
> element types are distinct.
> 
> The namespaces proposal serves only to provide a mechanism for making
names
> universally identifyable by associating them with Universal Resource
> Identifiers.  It is silent on any possible or speculative facilities for
> defining syntax or semantics.
> 
...

>> "Each type in the All Element Types Partition has an associated namespace
in
>> which appear the names of the unqualified attributes that are provided
for
>> that element. This is a traditional namespace because the appearance of
>> duplicate attribute names on an element is forbidden by XML 1.0. The
>> combination of the attribute name with the element's type and namespace
name
>> uniquely identifies each unqualified attribute."


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