Namespaces and XML validation

[David Megginson]

Peter Murray-Rust writes:

 > I know it's a slack time of year but it's catalysed (in my mind) by
 > the XML DevCon in Montreal in 12 days time. It would be nice to get
 > a feeling as to what activities people are thinking of for
 > implementing namespaces. So far we have had a few suggestions,
 > particularly James Clark, John Cowan, David Megginson and the
 > XSchema group. If DavidM reads this, it might be useful if he can
 > suggest how SAX might react to namespaces...

I'm looking forward to talking with as many of you as possible during
the XML Dev Day(s) in Montreal.  I first raised the issue of SAX and
namespaces on XML-Dev a few weeks ago -- after reading dozens of
postings and private messages, I am convinced that the only clean
solution is to define a special data type for two-part names,
something like the following:

  package org.xml.sax;

  public interface Name 
  {
    public String getURI ();
    public String getLocalName ();
  }

This, however, is the easy part; the hard part is figuring out how to
work this into SAX.  Here are some of the problems

1. How should SAX make the prefix map available to applications?  One
   option is to create a new handler type, called NamespaceHandler:

     public interface NamespaceHandler
     {
       public void startNamespaceScope (String prefix, String uri);
       public void endNamespaceScope (String prefix);
     }

   Another option is to create a new type of object called a Namespace
   Resolver:

     public interface NamespaceResolver
     {
       public Name resolveIndependentName (String name);
       public Name resolveDependentName (String name);
     }

   This could be set by the NamespaceHandler:

     public interface NamespaceHandler
     {
       public void setNamespaceResolver (NamespaceResolver resolver);
     }

2. Should DocumentHandler be replaced or extended?

3. Does AttributeList now require a two-part lookup key, or should it
   stick to the unresolved (one-part) names?

4. Is namespace processing a core SAX service or a filter on top of
   SAX?


All the best,


David

-- 
David Megginson                 david at megginson.com
           http://www.megginson.com/

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