xml-dev - Re: Re:Automating Search Interfaces"

[David Megginson <ak117@freenet.carleton.ca>]

Matthew Gertner writes:

 > One approach that really appeals to me is based on a two-pronged effort to
 > create standard tags *and* standard DTDs, and relies on the fact that there
 > is really a working mechanism for extending DTDs through inheritance (which
 > I guess is still not entirely the case).
 > 
 > Standard tags would be a bit of a hack, but probably very useful in a
 > pragmatic sense. For example, you might be able to say certain things about
 > a TITLE tag, or a PRICE tag, or whatever, just on the basis of the name,
 > regardless of the actual DTD being used. If these conventions were
 > well-known, this could be of great use when defining a new DTD (i.e. "Let's
 > call the tag PARAGRAPH and not PARA because this is what will be recognized
 > by search engines").

The idea is actually quite sound, but the implementation could be a
little cleaner.  Instead of relying on the element type name (which
may vary for different domains of information), why not have a
standard attribute (such as 'standard-doc') that gives the equivalent
standard name in the architecture.  That way, just as you write

  public class Cost implements Price {
  }

in Java, you can write

  <!ELEMENT cost (#PCDATA)>
  <!ATTLIST cost
    standard-doc CDATA #FIXED "price">

in XML, or even

  <cost standard-doc="price">xxx</foo>

This makes multiple inheritance easy:

  <!ELEMENT cost (#PCDATA)>
  <!ATTLIST cost
    standard-doc CDATA #FIXED "price"
    alt-doc CDATA #FIXED "value">

Now, that `cost' inherits from `price' in the standard-doc
architecture and from `value' in the alt-doc architecture.


All the best,


David

-- 
David Megginson                 ak117@freenet.carleton.ca
Microstar Software Ltd.         dmeggins@microstar.com
      http://home.sprynet.com/sprynet/dmeggins/

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