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   Re: [xml-dev] Finally, what if namespaces == document types ?

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  • To: xml-dev@lists.xml.org
  • Subject: Re: [xml-dev] Finally, what if namespaces == document types ?
  • From: "Clark C . Evans" <cce@clarkevans.com>
  • Date: Mon, 21 Jan 2002 18:24:14 -0500
  • User-agent: Mutt/1.2.5i

This is a neat way of looking at it.

| 1) Namespaces are just sets of names with no additional semantics...
|    In this scenario, schemas can span multiple namespaces because
|    the semantics of a document are defined by its schema, not the 
|    namespaces it uses.

| 2) Namespaces are meaningful. They are not only 50% of the document.
|    [In this scnerio,] an abstract schema is bound to the namespace, so
|    that it is possible to write code that depend only on the
|    namespace and its intrinsinc schema.

|    Note that this model could be easily extended to support multiple 
|    schema, depending on the first element encountered. In that case,
|    a namespace would have one abstract schema per element that can 
|    stand-alone or be embedded into a foreign document.

This second perspective seems to be close to what EHR wrote, that
is considering schema to be the property of an element rather than
of the document as a whole.

> You seem to be focusing on using schemas to validate *documents* as
> opposed to *elements*. If we refocus on elements rather than
> documents, the question is a lot easier to answer. Each element has a
> unique namespace. If that namespace has a RDDL document, then we can
> query that document to find a schema appropriate for validating that
> element.


| Now let's try to compare the two scenarii.
| - Scenario 1 and 2 seem equally powerful.

I'm not sure.  It seems to me that your first scenario requires
schema application to be done on a document "as a whole", while
the second scenario applies to parts of documents in a more 
fractal pattern.  Thus, I would read that the first scenario 
requires a third schema C as a composition of schema A and B,
while the second scenerio allows for a more dynamic composition
of schema.   I'm also wondering if the last scenerio is unworkable
for this very reason (dynamic composition).  It seems that a 
schema wants to give a fixed interpretation for an element; however,
the meaning of an element most certainly depends upon its context.

| In the current state of XML specifications and standards :
| 1) namespace != document type, except maybe for XML Schema which has a
|     different belief
| 2) RDDL cannot be used to obtain schemas for a given XML document, so we
|    have to create a document type
| 3) An alternative to the document type creation is to play a what-if 
|    game  about 'namespace==document type'. Scenario 1 is 
|    'namespace!=document type, so let's create document types'. 
|    Scenario 2 is 'namespace==document type, so what is XML becoming ?'.

Kind Regards,


Clark C. Evans                   Axista, Inc.
http://www.axista.com            800.926.5525
XCOLLA Collaborative Project Management Software

----- End forwarded message -----

Clark C. Evans                   Axista, Inc.
http://www.axista.com            800.926.5525
XCOLLA Collaborative Project Management Software


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