> -----Original Message-----
> From: J.Pietschmann [mailto:]
>
> 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.
