Why doesn't XML have Bag?

Andrew McNaughton andrew at squiz.co.nz
Fri Mar 26 14:12:35 GMT 1999

> Matt,
> Then let me ask another question - why do DTDs not allow me to specify
> an unordered list of elements?  For example, 
> <!ELEMENT Kitchen RDF:Bag(Sink, Stove, Refrigerator)>
> With this notation I am trying to indicate that an XML document that
> conforms to this DTD must have a <Kitchen> element which has three child
> elements - <Sink>, <Stove>, and <Refrigerator>, and these child elements
> can be in any order.  Isn't this a useful thing?  I have had a number of
> times where I wish that I could do this.

Is it a useful thing?  It might be nice for humans entering the data to be unconstrained in the order in which they can enter data, but if you know exactly what elements must exist within kitchen, then does it limit you to pre-define the order they appear in the document.

I suppose if you want the order to denote something about the position of the elements within your physical kitchen, then you've lost something, but attributes are probably a better solution for storing this information about the elements within your kitchen.

Andrew McNaughton 

Andrew McNaughton
andrew at squiz.co.nz

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