RQTS : tag order
Robert A. (Bob) Morris
ram at CS.UMB.EDU
Mon Dec 13 11:10:49 CET 1999
Gregor Hagedorn writes:
> Date: Mon, 13 Dec 1999 16:21:15 +0100
> From: Gregor Hagedorn <G.Hagedorn at bba.de>
> To: TDWG-SDD at usobi.org
> Subject: Re: RQTS : tag order
> Bob Morris wrote:
> > Here's a proposed requirement for data exchange, brought home by one
> > of Leigh's examples:
> > <RQT> It should be possible from the data itself, perhaps together
> > with external resources to which it refers, for software to determine
> > whether the order matters for any collection of tags in the
> > data.</RQT>
> I agree, especially that the software should be able to determine it.
> Regarding XML, tags, and DTDs, I believe, the assumption is that
> order does not matter, wherease an order can be imposed on attributes
> within a tag, correct?
No, it is exactly the opposite. A DTD imposes an order on tags, but attributes
However, the November 5 working draft of XML Schema provides
mechanisms for settling tag order questions. XML Schema is a language for
specifying tag constraints in XML itself, rather than in the DTD
language which is not itself a special case of XML. Among other
things, it provides strong data typing, including the ability to
restrict the range of data, whereas in a DTD the only primitive data
type is a string.
It is slightly plausible that XML Schema would actually provide a good
data modeling language independent of whether one wished to use it as
an interchange language or as the native data store.
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