Gregor Hagedorn writes:

Date: Mon, 13 Dec 1999 16:21:15 +0100 From: Gregor Hagedorn G.Hagedorn@bba.de To: TDWG-SDD@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 are unordered.

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.

Bob Morris