- From: Philip Aker <philip.aker@shaw.ca>
- Date: Mon, 26 Jan 2009 06:26:56 -0800
- To: Michael Kay <mike@saxonica.com>
- Cc: 'Pete Cordell' <petexmldev@codalogic.com>, xmlschema-dev@w3.org
On 2009-01-26, at 05:32:31, Michael Kay wrote:
>> Not being an XSD expert, maybe my question is "why can't the
>> content ordering possibilities be specified as a regex-like
>> pattern?".
> One of the criticisms of DTDs, which XSD attempted to address, was
> that DTDs
> were written in a non-XML-like syntax which made it difficult for
> applications to process the information (and difficult in many cases
> for
> authors to remember the syntax). The thinking was that by using an
> XML-based
> syntax, the data would be much more accessible; and some argued that
> verboseness doesn't matter because authors would be working with
> specialized
> tools rather than editing at the source level.
I see. I believe that syntax integrity is good. However, my thinking
is that xs:pattern regexen are part of vocabulary, and elements,
including user-defined element types, are now supported data types.
Therefore a pattern can express element ordering possibilities using a
subset of regex notation. So this mythical 'collection' model group
would subsume 'all', 'choice', and 'sequence' by having the ordering
specified in a 'pattern' attribute provided it could contain itself.
<xsd:collection pattern="(b|c|x|xsd:collection){0,}, a{2}, (a|b|c|x)
{0,}">
…
</xsd:collection>
This would result in a simplification of both the specification and
implementation and probably be more cost efficient in the long term.
> There is continued interested in defining a less verbose syntax.
> However, the XML Schema WG is very stretched for resources.
If I had the money, I'd send you all millions. XSD is a truly worthy
endeavor.
Philip Aker
echo astwta@lvpc.dslh@nl | tr a-z@. p-za-o.@
Democracy: Two wolves and a sheep voting on lunch.
Received on Monday, 26 January 2009 14:27:38 UTC