- From: Tim Bray <tbray@textuality.com>
- Date: Sun, 20 Oct 1996 19:40:38 -0700
- To: w3c-sgml-wg@w3.org
The existence of an "induced" DTD when one is not provided has been a source of much lively discussion, on the WG, the ERB, and between XML's co-editors. There are two questions that are material in the context of non-provided DTD's: 1. Is there in fact an induced DTD which can be said to control or even affect the behavior of an XML processor? 2. Does such an induced DTD serve a useful didactic purpose in explaining the behavior of an XML processor.? The answer to #1 is clearly "no". Charles provided an example that exactly matched <!element doc (p,p)>, but unless there have been some huge advances in tree simplification theory that I haven't heard about, deriving the minimal DTD [for any useful definition of minimal] for most nontrivial real-world documents proves in practice to be horribly difficult and not all that useful. Obviously, a DTD that declares all elements to be ANY and all attributes to be CDATA fills the bill, but it's hard to see how that controls or even affects the behavior of an XML processor. #2 is more arguable, but to a person who is still learning what a DTD is and means, the didactic value is probably negative; to a person who does understand, it's easier to explain well-formedness with assertions such as "There is a root element. Tags balance. EMPTYs are declared." The reason why this debate is worth having is practical: should the XML spec contain any discussion of induced DTD's, yes or no? I think not. Cheers, Tim Bray tbray@textuality.com http://www.textuality.com/ +1-604-488-1167
Received on Sunday, 20 October 1996 22:40:55 UTC