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Re: Namespace prefixes optional?

  • From: james anderson <James.Anderson@m...>
  • To: xml-dev <xml-dev@i...>
  • Date: Fri, 07 Jan 2000 16:28:23 +0100

all kind prefixes
David Megginson wrote:
> 
> james anderson <James.Anderson@m...> writes:
> 
> > a. How does one do attribute defaulting in situations where the
> > namespaces matter. That is, in situations where one can't just treat
> > the document as if it were "xml-1.0-plain".
> 
> Declare the attribute -- it is irrelevant whether Namespaces matter or
> not.  Or is your question "how can you preserve an attribute default
> after a round trip through a processor that doesn't preserve the
> original Namespace prefixes"?
> 

No, that is not the issue. Namespaces matter only when an identity based on
prefixes would not have been sufficient. Otherwise, except for the ability to
bind xmlns="<uri>", the namespaces are redundant. In these cases where the
prefixes are not identical, that is, where the namespaces matter,
xml-1.0+namspaces, as ratified, doesn't work.

> 
> > b. How can one uphold the constraint, that the set of valid
> > "xml-1.0+namespaces" documents is identical with the set of valid
> > "xml-1.0-plain" documents. Mr Waldin's question is one case in point.
> 
> I'm not sure what you mean.
> 
> If you're using "valid" the same way as the XML 1.0 spec does, then
> the set of valid documents that happens to contain Namespace
> declarations is a strict subset of the set of all valid XML 1.0
> documents; in other words, they are not identical.
> 
> ... it is possible to have a document that is well-formed but
> not valid XML 1.0, but still conforms to Namespaces, RDF, or XLink
> (though not XHTML, which requires validity for strict conformance).

Hmm, we now have the class of invalid, but namespace conformant documents. I
recall hearing rather clear assertions to the contrary post-REC. Evidently the
winds have changed on this question.

> 
> > c. How does one specify an identity between a "name which is in no
> > namespace" and a "name in a namespace as declared in a
> > schema". Perhaps I'm just narrow-minded, but I sense a potential
> > contradiction in this notion.
> 
> This is an interesting problem, but what does it have to do with
> Namespaces?  All the Namespaces REC does is specify how to create
> elements and attributes with two-part names, like you can with methods
> or variables in Perl and Java (Namespace == package).

Not entirely. The REC is the origin of the "names which are in no namespace" concept.

> [discussion elided 'cause the questions have nothing to do with semantics.]
> 
> > These for starters. They follow from the root problem, that the REC
> > did ratify a complete model for the domain which it describes. It
> > was most disappointing to observe the extent to which the appendix
> > was disavowed. Were one to have taken something of that sort
> > seriously, such issues may have come to light, rather than being
> > "left to the application".
> 
> For "left to the application" substitute "left to higher-level specs".

Where higher-level is in the plural I hesitate to distinguish between the two
in the case of xml and namespaces. Remember Mr. Bray's frequent reference to
the "difficult things" truism. I would not be surprised that they both reduce
to naming.

> People were already preparing to start work on an XML Schema spec, and
> it didn't make sense for Namespaces to do a half-assed job trying to
> do part of schema's work for it and then leaving the schema people
> with all kinds of constraints.

I would have thought that names and schemas should have been separable.
They have been in other domains.

> 
> Good specifications are layered, with each one accomplishing a single,
> well defined task.  The Namespaces spec set out to answer the question
> "How do you represent a two-part name in XML 1.0 syntax?", not "How do
> you solve every possible problem with inheritance, identity, and
> validation in XML?"
> 

With which, with the exceptions of "identity" my questions remain, unconcerned...


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