Re: [Bug 11354] Mentions of "override" outside of the override section

On Mar 7, 2011, at 5:04 PM, bugzilla@jessica.w3.org wrote:

> http://www.w3.org/Bugs/Public/show_bug.cgi?id=11354
> 
> Michael Kay <mike@saxonica.com> changed:
> 
>           What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                 CC|                            |mike@saxonica.com
> 
> --- Comment #6 from Michael Kay <mike@saxonica.com> 2011-03-08 00:04:43 UTC ---
>> "Since the overridden source declaration is overridden, 
> it isn't used to try to create or identify any components, so its errors 
> do not need to stand in the way of identifying the schema to be used
> in validating the document.".
> 
> Oh dear, ghastly thought. Suppose someone writes
> 
> <xs:element name="abc" type="!!**!!**!!**!!"/>
> 
> and then overrides this. Is the processor actually not allowed to report an
> error?
> 
> I would resist such an interpretation.


I think it depends on what you mean by "report an error".

If you say "There seems to be something wrong there", I don't think
you are violating the XSD spec.

If you say "This schema document is not schema-valid against the
schema for schema documents", that's a true statement, though you
are not required to check schema validity for the document before
pre-processing it. 

(Or are you?  The transformation specified is schema-aware, so
to run it as written you do need to schema-validate it.)

If you say "I can't identity a schema here because the input to the
override pre-processor was not a conformant schema document" -- that
is, if you say that what you've found is an error in the narrow sense of 
being a failure to conform to the spec, I think you may be on thin ice.

If your error messages don't make clear whether they are reporting
places where something fails to conform to the spec, or just
things you think the user ought to know, then there will be some
uncertainty about whether you're doing the right thing or not.

All of this is complicated by the fact that the transformation in the
appendix is schema-aware; if that's what we really mean to say,
then you seem not only to be allowed but to be required to check
the input document for schema validity. But that contradicts the
statement of the spec that it is the output, not the input, which must
be valid.

So we have a contradiction that we need to resolve.

-- 
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* C. M. Sperberg-McQueen, Black Mesa Technologies LLC
* http://www.blackmesatech.com 
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Received on Tuesday, 8 March 2011 01:02:45 UTC