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Re: Processing external DTD subset as part of DTD validation

• To: Mikko Saesmaa <saesmaa@m...>
• Subject: Re: Processing external DTD subset as part of DTD validation
• From: Elliotte Harold <elharo@m...>
• Date: Mon, 10 Apr 2006 06:59:40 -0400
• Cc: xml-dev@l..., =?UTF-8?B?UGVra2EgS2lscGVsw6RpbmVu?=<pekka.kilpelainen@c...>
• In-reply-to: <Pine.A41.4.63.0604101302580.148506@m...>
• References: <Pine.A41.4.63.0604101302580.148506@m...>
• User-agent: Thunderbird 1.5 (Macintosh/20051201)

Mikko Saesmaa wrote:

> As far as we know, JAXP does not support the validation of DTDs
> directly. Our original idea was to wrap the DTD inside the
> prolog of a dummy document instance. The problem with this approach
> is that this way we would pass the declarations to the parser as an
> /internal/ DTD subset, which has different restrictions on the use of
> parameter entities than an external subset.

This came up recently on another list. It is possible to distinguish the 
internal from external DTD subset using a pure SAX parser, particularly 
Xerces. (Crimson has some bugs in this area.) The trick is to follow the 
entities and look for one named "[dtd]". That's the internal susbet. 
Here's how XOM does it:

     protected boolean inExternalSubset = false;

     // We have a problem here. Xerces gets this right,
     // but Crimson and possibly other parsers don't properly
     // report these entities, or perhaps just not tag them
     // with [dtd] like they're supposed to.
     public void startEntity(String name) {
       if (name.equals("[dtd]")) inExternalSubset = true;
     }


     public void endEntity(String name) {
       if (name.equals("[dtd]")) inExternalSubset = false;
     }

That said, it might still be better to look at the native Xerces APIs if 
they suit your needs.


-- 
Elliotte Rusty Harold  elharo@m...
XML in a Nutshell 3rd Edition Just Published!
http://www.cafeconleche.org/books/xian3/
http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim

• References:
  • Processing external DTD subset as part of DTD validation
    • From: Mikko Saesmaa <saesmaa@m...>

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