RE: XML 1.0 - Element order significance

[Danny Ayers <danny@panlanka.net>]

Hi,
I asked a similar question a while ago - if I remember correctly, the XML
Rec itself has nothing to say about element order, but it is included in the
InfoSet Rec :

http://www.w3.org/TR/xml-infoset

In practice, a parser will usually pick up the elements in order, but unless
explicitly specified, doesn't have to. I've no idea what XML Schemas have to
say on the matter.

Hopefully some kind soul will confirm/negate the stuff above and fill in the
blanks, though it'll probably come in Haiku form.

Cheers,
Danny.

<- -----Original Message-----
<- From: Henry S. Thompson [mailto:ht@cogsci.ed.ac.uk]
<- Sent: 22 January 2001 15:10
<- To: Rawlings, Matthew BGI UK
<- Cc: XML Developers List
<- Subject: Re: XML 1.0 - Element order significance
<-
<-
<- "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?
<- >
<- > <brothers>
<- > 	</matthew>
<- > 	</james>
<- > 	</luke>
<- > 	</david>
<- > </borthers>
<- >
<- > 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 [1]) 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,
<-
<- ht
<-
<- [1] http://www.w3.org/XML/Schema.html
<- --
<-   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: ht@cogsci.ed.ac.uk
<- 		     URL: http://www.ltg.ed.ac.uk/~ht/
<-