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On Mon, 4 Jun 2001, James Clark wrote: > > Grammars should be an implementation technique, > > not the nub of the question. I just had a comment on this -- I will mention my view point -- I think xml schemas have several properties that I think are useful for data modeling -- I think even if in the past we did not have them, i think these are *very* useful and convenience features -- one of them is closure under union -- i think this is very useful. also i think xml technologies are quite important and are slowly making their inroads into academic books -- I think the undergraduate book for formal language theory -- by Hopcroft, Motwani and Ullman, right now speak of DTDs (they actually do not mention tree languages/grammars probably because "unranked" tree languages were not the first to be studied, and probably not as popular as we assume them to be, in stead they mention them as context free languages and do *not* mention that DTDs are closed under intersection -- anyways, these come later and have to be changed). I think if xml schemas are to be understood in academia, they should be taught as regular tree/hedge languages -- I think that can be the only underlying principle. regards - murali.
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