Why doesn't XML have Bag?

[Paul Janssens]

Frank Boumphrey wrote:
> 
> In SGML you can put
> (a&b&c) whicch means that eachelement must appear only once but in any
> order.
...
> 
> My understanding was that it was ommited because of the requirement
> 
> "XML software shall be easy to write"
> 
> It takes only a few lines of C code to validate the second requirement but a
> LOT more to validate the first.
> 

How about expanding it as you parse the DTD (bottom-up coding)

node ampersand(node a node b) {
   return or(concat(a,b),concat(clone(b),clone(a)));
}

that's just adding three lines to your code.

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