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Re: can dtds be extended?

• From: Wayne Steele <xmlmaster@h...>
• To: mbrown@i..., xml-dev@l...
• Date: Wed, 12 Sep 2001 13:27:25 -0700

Kinda Sorta.

You'll have to use an "Internal Subset" to do this.
Here's an example:

---standard.dtd---
<!ELEMENT E (#PCDATA)* >
<!ATTLIST E
   a CDATA #REQUIRED >
------------------

Now say you wanted to include or inherit this DTD, but add a 'b' attribute 
on the 'E' element. Your instance document might look like:

---------------------
<?xml version="1.0" ?>
<!DOCTYPE E SYSTEM "standard.dtd" [
   <!ATTLIST E b CDATA #IMPLIED >
]>
<E
   a="i am a required attribute"
   b="I am an new attribute
/>
---------------------

If things end up getting too complicated, you can use External Parameter 
Entities to do much the same thing, and more.

-Wayne Steele




>From: Matt Brown <mbrown@i...>
>Reply-To: mbrown@i...
>To: xml-dev@l...
>Subject:  can dtds be extended?
>Date: Wed, 12 Sep 2001 12:02:13 -0700
>
>Hi,
>I am using a published DTD (PMML) and need to add attributes to one of the
>elements. Is there any way I can do this, ie, extend the DTD in a way such
>that I can include extra information for my needs while still conforming to
>the published standard? For example, is there any way I can overwrite an
>element or attlist in an xml doc with a new one of the same name with more
>attributes? Can I reference 2 DTD's an include a smaller "DTD addition" 
>with
>my xml? Is there any way to support inheritance in XML?
>thanks,
>matt
>
>
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