Re: [relax-ng] Limitation in the compact syntax

[James Clark <jjc@jclark.com>]

> Not utterly.  It's just that embedded RNG after roundtripping will not
> be presented as clearly as it might be, not that it won't *work*.
> Converting back to XML will get you the same semantics as before,
> whatever they might be.

I don't see how this is going to be acceptable behaviour for a user.  If

- a user were maintaining the source in the compact syntax
- they were making significant use of your proposed feature
- they wanted to manipulate the source using XML tools (e.g. to rename a 
definition)

I don't believe they would find it acceptable if all their embedded 
patterns got turned into generic annotations.

So I believe that in practice users would have to make a choice between 
making use of your feature and being able to round-trip in a useful way.

>> For example, the
>> compact syntax represents both
>>
>>   <element name="foo"><empty/></element>
>>
>> and
>>
>>   <element><name>foo</name><empty/></element>
>>
>> by
>>
>>   element foo { empty }
>>
>> and all of
>>
>>   <choice><ref name="foo"/></choice>
>>   <group><ref name="foo"/></choice>
>>   <interleave><ref name="foo"/></interleave>
>>
>> by
>>
>>   (foo)
>>
>
> Which is precisely why exact XML > compact > XML roundtripping does not
> work even now, though the semantics are in fact preserved by this.

I guess it depends what you mean by "work".  I mean "behaves in a way that 
is likely to be acceptable to a user".  I think in this sense XML 
roundtripping does work.

>> In such a case,
>> the ooRNG schema might well conform to the RNG schema.   However, it
>> wouldn't semantically be RELAX NG.  If I fed it to jing -c it, wouldn't
>> work.  It would need to be translated first.
>
> Of course it would; first from the compact syntax to the XML syntax via
> Trang, and then from the XML syntax to pure RNG via XSLT.

Right, which is why this is out of scope.  We are designing a syntax for 
RELAX NG, not for random XML vocabularies that can be translated into RELAX 
NG.

James