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Re: ASN.1 => XML Schema questions

From: Dan Connolly <connolly@w3.org>
Date: Tue, 26 Jun 2001 16:19:33 -0500
Message-ID: <3B38FC65.2FBC4C8B@w3.org>
To: "K.Kawaguchi" <kohsukekawaguchi@yahoo.com>
CC: Geoff Elgey <elgey@dstc.qut.edu.au>, xmlschema-dev@w3.org
"K.Kawaguchi" wrote:
> 
> > I know that N! alternatives sounds daunting when performing schema
> > validation -- is this why <all> cannot have repetitions or be nested
> > within a <sequence> ?
> 
> There are algorithms that can validate <all> nested within <all>, or
> whatever (see http://www.thaiopensource.com/relaxng/jing.html for
> example), but it's just that W3C XML Schema decided not to allow them
> for some reason.

I'm pretty sure the reason is that in W3C XML Schema validation,
the result includes not just a "yes, this is valid"/"no, not valid"
but also "and this part of the input matched this part of the
schema" i.e. "it has this type, is associated with this annotation"
etc.

[I wish we had revised our requirements document to point
this out more clearly; it's a requirement that motivates
a lot of decisions that otherwise don't look nice.]

> So your options are either
> 
> - stick to W3C XML Schema and make a compromise by using (a|b)* rather
>   than (ab|ba)*.
> - or switch to another schema language that allows you to express what
>   you want.

Keep in mind that the other languages won't give you type/annotation
info as a result of checking.

> regards,
> ----------------------
> K.Kawaguchi
> E-Mail: kohsukekawaguchi@yahoo.com

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Tuesday, 26 June 2001 17:19:40 GMT

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