OASIS Mailing List ArchivesView the OASIS mailing list archive below
or browse/search using MarkMail.


Help: OASIS Mailing Lists Help | MarkMail Help



   Re: [xml-dev] Why datatypes?

[ Lists Home | Date Index | Thread Index ]

Gustaf Liljegren <gustaf.liljegren@xml.se> writes:

> Ever since XML Schema started to evolve and the talk about datatypes in XML
> took off, I've been wondering secretly why XML validation needs the concept
> of datatypes at all. XML is a plain text format, so content validation in
> XML should be no different from regular pattern matching. Or why should it?

So that you can appeal to the semantics of the datatype in expressing
constraints, in particular range constraints.  You _could_ write a
regexp for numbers between 95.5 and 99.8, to two significant digits,
but I don't think you'd want to.  I don't think you _could_ write a
regexp for dates between 2002-02-15 and 2003-02-15.

Appealing to the semantics makes these easy -- just give the max and

Similar argument for defining equality in wrt the values, so that a
numeric type will compare 3 and 3.0 as equal, for example.  Equality
arises in schemas in keys and in enumerated types.

  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2002, 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/
 [mail really from me _always_ has this .sig -- mail without it is forged spam]

  • References:


News | XML in Industry | Calendar | XML Registry
Marketplace | Resources | MyXML.org | Sponsors | Privacy Statement

Copyright 2001 XML.org. This site is hosted by OASIS