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At 12:37 PM 11/22/00 -0800, Joe English wrote: >PUBLIC ID resolution doesn't need to be universally deployed >for it to be useful. In many scenarios, out of all the software >that might be used to process an XML document, only one -- the >document's author's validator -- really needs PUBLIC ID support. >All other document consumers should be able to ignore the ><!DOCTYPE ...> declaration entirely as long as the DTD >makes no essential InfoSet contributions. Unfortunately, the use of URNs for SystemLiterals makes PUBLIC a more important option than it is when URLs are used. Processors which lack PUBLIC identifier processing and which receive documents using URNs as SystemLiterals are pretty much stuck, since they can't get to the DTD at all. _If_ the DTD makes no essential Infoset contributions, the DTD doesn't matter at all except to provide constraints. However, since DTDs frequently make Infoset contributions (and the IANA registration document sets no such limitations), processors have no way of knowing whether or not the DTD is required for proper processing. I guess this is familiar ground, since the option for non-validating parsers to ignore external resources has similar ramifications, but it seems to drive it even deeper into the heart of XML by making even validating parsers unreliable. Simon St.Laurent XML Elements of Style / XML: A Primer, 2nd Ed. XHTML: Migrating Toward XML http://www.simonstl.com - XML essays and books
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