Re: [xml-dev] XML spec and XSD

["G. Ken Holman" <gkholman@CraneSoftwrights.com>]

At 2009-11-15 17:15 +0530, Mukul Gandhi wrote:
>    Saying that something like, xs:redefine isn't implemented
>consistently across different XSD processors, IMHO doesn't justify
>condemning XSD completely.

I cited it only as an example.  Forgive me if my comments came across 
as otherwise.

>I think, even a correct implementation of
>say, xs:redefine on one or two processors is good enough.

But are there two implementations that are the same, and if they are 
the same, are they the "correct implementation" you cite?  I believe 
this is the root of the issue:  it isn't that vendors have 
implemented the specification incorrectly, it is that the 
specification is unclear enough that each vendor believes they have 
implemented it correctly yet end up with different results.  There 
are no "bugs" that can be identified and repaired in each vendor's 
incompatible work because there is no agreement on the interpretation 
of the specification as written.

The validation semantics for W3C schema are written in prose.

The validation semantics for RELAX-NG are written in formal 
unambiguous notation, guiding all implementers to a formally correct 
implementation if they properly implement the documented 
semantics.  Of course they can implement bugs, but because of the 
formalisms, the bugs can be identified as such without debate.

>Sometimes,
>vendors create differences in implementations to differentiate (I am
>not really sure though, if that's true. At least the base standard
>should be implementable).

And that is my very point:  yes, it should be written so as to be 
implementable by all without ambiguity.  Practice has revealed this 
is not the case for W3C Schema.

>I am not trying to be getting into a mud sludge game between computer
>languages, or to express sarcasm to any XML validation language. I
>appreciate, efforts of anybody taking pains to design anything like
>these languages, and implement them.

Indeed.  And please forgive me if my comments come across as sarcasm 
of W3C schema, as I have been trying very hard to be objective so as 
to illustrate the concerns with concrete examples.  It is not my 
intention to obfuscate the issues with mud, but to clarify the issues 
by citing identifiable sources of concerns with the 
technology.  Those in this debate who have not supported W3C schema 
have been speaking up in the interests of all XML users who may have, 
themselves, been misguided regarding the technology (intentionally or 
unintentionally).

. . . . . . . . . . . . . Ken

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