[relaxng-user] Re: Jing and libxml2 is right, Trang is wrong

[Eric van der Vlist]

On Sat, 2004-03-06 at 09:12, David Tolpin wrote:

> 2) I tend to disagree with James. Either implicit grouping is not
> allowed anywhere, or it is consistently allowed; 
> 
> start = foo,bar
> 
> is perfectly correct and normally used in nested grammars. Nested
> grammars are very useful in conjunction with parentRef elements.
> 
> Trying to fix a hypothetic bug James introduced a real one.

I have been surprised by this limitation too and that's why I had asked
the question. My "natural" expectation was that the content model of
<start/> would be coherent with the content model of <define/> since
these two patterns are really very similar in behaviour.

> 3) In cases where 
> 
> start = foo, bar 
> 
> is a bug,
> 
> <start>
>   <ref name="foo"/>
>   <ref name="bar"/>
> </start>
> 
> does not have a chance to be misused as it were a choice, because
> this pattern is forbidden in top-level grammars.
> 
> Cases where
> 
> start = foo, bar
> 
> is correct is used in nested grammars; and in most cases nested
> grammars are used by people who know what they are doing.
> 
> I think this artificial limitation should be lifted.

That would be my feeling too, but it's really difficult to tell what's
the least confusing...

Misusing and implicit <group/> for a <choice/> would leave to schemas
that would be valid but behave in an unexpected manner (for the author
who would have made the error) while this restriction raises a schema
error which cannot be ignored and that can be considered safer.

Eric
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Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
(ISO) RELAX NG   ISBN:0-596-00421-4 http://oreilly.com/catalog/relax
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