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Parameter entities vs. GI name groups

From: Eve L. Maler <elm@arbortext.com>
Date: Thu, 19 Jun 1997 08:30:37 -0400
Message-Id: <3.0.32.19970619083036.00b63100@village.doctools.com>
To: w3c-sgml-wg@w3.org
Cc: elm@arbortext.com
The ERB, in its meeting yesterday, discussed the issue of parameter
entities in XML.  We are *strongly* leaning towards voting to remove
parameter entities entirely *from V1.0* as long as GI name groups are
reinstated in ELEMENT and ATTLIST declarations:

<!ELEMENT (a|b|c) ...>
<!ATTLIST (x|y|z) ...>

We plan to vote on this at next Wednesday's meeting; your input is welcome.

The reasons to prefer GI name groups:

o Many of the uses of parameter entities that new DTD writers and simple 
  DTDs are likely to want can be replaced by GI name groups: synchronizing 
  the content models or attribute lists of elements

o GI name groups add extremely little complexity to XML processors

o Now that we have multiple ATTLISTs, GI name groups have quite a bit more
  power than they used to (e.g., you can add a set of attributes to "all
  the list elements," and then add a unique attribute to only one of the
  elements)

o GI name groups give us the syntax (if not the semantics) to do a kind of
  element subclassing, where all the elements in a "class" have the same
  characteristics

One consequence:

o Existing DTDs and any new complex DTDs that need parameter entities would
  have to be transformed to resolve parameter entities before XML delivery
  (note that several existing tools, such as NormDTD, do this)

	Eve
Received on Thursday, 19 June 1997 08:28:06 EDT

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