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Re: XML 1.0 - Element order significance
- From: firstname.lastname@example.org (Henry S. Thompson)
- To: "Rawlings, Matthew BGI UK" <Matthew.Rawlings@barclaysglobal.com>
- Date: Mon, 22 Jan 2001 09:09:38 +0000
"Rawlings, Matthew BGI UK" <Matthew.Rawlings@barclaysglobal.com> writes:
> Is element sequence order significant in XML 1.0? I can see no clear guide
> from the specification - does omission mean significant or not significant?
> Given the example below is it reasonable if told in advance to attach
> significance, .e.g age order or grade order, to the set of brothers?
> I understand that attribute sequence order is not significant in XML. This
> is clear to me from the specification.
Without looking at the DTD you can't tell. Somewhat
counter-intuitively, if the DTD says:
<!ELEMENT brothers (matthew,james,luke,david)>
then you can infer that order is _not_ significant, since the grammar
gives you no choice.
If on the other hand it says:
<!ELEMENT brothers (matthew|james|luke|david)*>
then you can infer that order _may_ be significant. Unfortunately,
you get the possibility of multiple instances as well.
In SGML (and in XML Schema ) you can say
<!ELEMENT brothers (matthew & james & luke & david)>
which again allows you to infer that (since the elements can occur in
any order) that order _may_ be significant.
Hope this helps,
Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
W3C Fellow 1999--2001, part-time member of W3C Team
2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
Fax: (44) 131 650-4587, e-mail: email@example.com