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> -----Original Message----- > From: J.Pietschmann [mailto:j3322ptm@y...] > > Robert DiFalco wrote: > > How do most people feel about imposing a sibling element order > > significance? > ... > > However, it seems harder to write parsers that process elements in a > > random ordering. So often, an arbitrary order is imposed (presumably) to > > make parsing easier. > > It is hard to write a DTD with elements which takes a somewhat > larger number of different child elements in arbitrary order > but each at most once or exactly once. > For me, that's enough to introduce an order constraint. It's not hard, just ugly: (for each child B, C, D at most once) <!ELEMENT A ((B)|(C)|(D)|(B,C)|(B,D)|(C,D)|(C,B)|(D,B)|(D,C)|(B,C,D)|(B,D,C)|(C,B,D) |(C,D,B)|(D,B,C)|(D,C,B)) > That said, this is enough to make order constraints required rather than useful, with 20 children this becomes so tedious the errors are almost guaranteed. Martin.
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