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Re: xs:choice and xs:sequence question

From: George Cristian Bina <george@oxygenxml.com>
Date: Thu, 12 Jan 2006 20:50:38 +0200
Message-ID: <43C6A4FE.3040107@oxygenxml.com>
To: Michael Kay <mike@saxonica.com>
CC: d_a_carver@yahoo.com, xmlschema-dev@w3.org

Hi Mike,

I do not see reportig the place of the error in the XML Schema spec and 
formulating a good error message as excluding each other. I agree that 
some parts of the specification are not easy to read, however this is 
not a subtitution of the error message, it is an enhancement to that.

I find this useful especially when people say: well that schema engine 
reports that my schema is valid while Xerces[1] or oXygen reports this 
error. Pointing to the schema specification saves a lot of time as you 
have immediatelly access to the place in the specification that is 
related with the error. If it is difficult to read that it is a lot more 
difficult to take the whole schema specification and first look for the 
place related to the error and then read that.

[1] oXygen uses currently Xerces 2.7.1 for validating XML schema files. 
In the next release we added the possibility to use most of the XML 
Schema processors: Saxon SA, XSV, MSXML 4.0 and .NET, LIBXML, IBM SQC.

Best Regards,
George Cristian Bina
<oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger

Michael Kay wrote:
>>oXygen reports the error with a link to the specification 
>>related with that:
> A tangential remark: I wonder how useful this is? I know Appendix C says
> that validity errors "should" be reported citing the chapter and verse of
> the spec, but is there really any serious prospect that the average schema
> author will get any value from this? Your link points to the sentence:
> "A content model must be formed such that during .validation. of an element
> information item sequence, the particle component contained directly,
> indirectly or .implicitly. therein with which to attempt to .validate. each
> item in the sequence in turn can be uniquely determined without examining
> the content or attributes of that item, and without any information about
> the items in the remainder of the sequence."
> I suspect most users can't even parse the syntax of this sentence, let alone
> understand what it means.
> I decided in Saxon that there wasn't any point in referring people to the
> spec, and instead try to explain what's wrong in my own words. In this case
> you will get a message to the effect: "the content model is ambiguous,
> <elementname> appears in more than one place".
> Any views on this from users?
> Michael Kay
> http://www.saxonica.com/
Received on Thursday, 12 January 2006 18:50:18 UTC

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