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Processing external data entities

From: David Megginson <>
Date: Wed, 26 Mar 1997 20:37:02 -0500
Cc: James Clark <>
[I've CC'd this message to James Clark, in case he's not on the list yet.]

Tony Graham writes:

 > David Megginson writes:

 >  > In the style language, it is easy to handle
 >  > 
 >  >   <listing source=code>
 >  > 
 >  > using
 >  > 
 >  >   (element LISTING
 >  >     ...)

 > Truth to tell, I (and possibly several others) have yet to have to
 > handle your first case of "<listing source=code>".  Can you explain
 > how it would be done?

I had assumed that I would use something like this:

  (element LISTING
    (let ((ename (attribute-string "SOURCE"))
          (nname (entity-notation ename)))
      (make external-graphic
        entity-system-id: (entity-system-id ename)
        notation-system-id: (notation-system-id nname))))

It would require only minor modifications to the Jade RTF backend to
support special handling for a source-code-listing notation.  Is this
a legitimate use of the 'external-graphic' flow-object class?  If not,
we could implement some extensions to the expression language for
read-only file input, since they would be side-effect free.

All the best,


David Megginson       
Microstar Software Ltd.
University of Ottawa