Re: Moving on (was Re: URIs quack like a duck)

Tim Berners-Lee> I don't think this is a time for compromise.
Tim Berners-Lee> Yes, it is a compromise.

Hmmm.

> * using relative URI references is  a bad idea, because existing software
>    does different things with them.

If it just does this, and doesn't actually forbid them then it has to
answer the question `what is the namespace name of the element marked
up as <x xmlns="x"/>' otherwise this whole discussion has failed.
It can't forbid them without orphaning a lot of existing documents.

> Software which absolutizes the URI-reference
> and uses the URI will be legal. So will software which compares as
> strings. 

That is already the case now. Obviously any software that is going to
retrieve any resource based on the namespace name is going to make an
absolute uri first. But still the namespace spec has to say what the
namespace name is for all conforming documents (even documents that
use features that are listed as unwise). Leaving this undefined
would be just a failure of the entire process of this list.


> XPath does not need to be re-issued as it will interwork, as relative
> URIs are excluded.

They are not excluded unless they are forbidden. While it is true that
applications layered over namespaces may retrieve resources using the
namespace name (and thus of necessity form an absolute URI first)
the DOM and xpath are software specifications that provide the
interface to ask the question asked above

`what is the namespace name of the element marked up as <x xmlns="x"/>'

So the dom, xpath, and the namespace spec all need to give the same
answer, even if the entire construct is deprecated.
I believe that the statement should be that the namespace name is as
defined in the current namespace spec, the literal interpretation
but that a warning should be made explicit that a) relative uri aren't
globally unique names, and b) some software will use the namespace
name as is and some will use the absolute uri obtained by combining
the namespace name with the document base uri, and thus surprising
results may trap the unwary.

> That would be a note.  I think that it might be a good idea to point out
> for example that
> - such a document is not mandatory
> - the document may include xml-schema

agreed. The fact that tying schema in particular to namespaces is a
bad idea is a separate issue unrelated to this namespace uri issue,
and in theory it might be the case that some namespace has (and only
ever will have) one schema, in which case it might make sense to put
the schema at the namespace uri. (I don't know of any namespaces for
which this is true, but that doesn't mean that none exist)

> - a document can contain xml-schema and also other information

That's not really the point, the other information is ignored by
the schema validator so the document works as a schema, but will
it work as an xsl stylesheet, or a dtd or a XDR schema or anything
else that you want to associate with the namespace? The answer is no
if the `other information' is second class compared to the schema
information and has to be in a format dictated by the schema spec.

David

Received on Friday, 2 June 2000 03:32:40 UTC