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   Re: Who can implement W3C XML Schema ?

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At 10:42 AM 3/21/2002 -0500, Kohsuke Kawaguchi wrote:

> > I am not saying we should abandon RELAX-NG. I like it, and would like to
> > see it gain market share. But I think that the XML industry as a whole is
> > *going* to be using XML Schema in the near future. Let's make the best 
> of it.
>If you think RELAX NG is better than W3C XML Schema, then isn't it your
>responsibility to say it loud?

I said that RELAX NG is more graceful and beautiful than XML Schema, but on 
balance, I think that each has advantages.

Here are some of the advantages of XML Schema:

1. For most people who use schemas, what they really need is datatypes. 
Otherwise, DTDs would meet most of their needs. Having the same set of 
built-in datatypes across all XML Schema implementations is a very good 
thing, IMHO.

2. Named typing is very efficient for parameter passing. The fact that 
named typing is used in XML Schema makes it easy to implement efficient 
parameter passing in XQuery. There are fancy ways to do similar things by 
computing tokens with forest automata, but they are not all that easy for 
most people to implement.

3. It's established and supported. If I want to solve a problem today with 
a representation that is supported by most of the tools I use, XML Schema 
is the obvious choice.

I suspect that most XML schema languages that support datatypes are pretty 
much interchangeable for most business needs. There are some areas where 
the advantages of a particular schema language may make a big difference, 
but they are probably relatively few.

As a basis for the XML Query type system, I think that the above factors 
outweigh the advantages of RELAX-NG. Since both activities are in the W3C, 
we probably don't have much choice anyway. And although I think we need to 
put some effort into improving XML Schema - including rewriting Part 1, 
redefining restriction, a bunch of bug fixes, etc - on balance, I do think 
that XML Schema is useful and usable. Perhaps I spent too many years 
writing too many lines of C++, which was certainly not a beautiful language.

>You wrote as if you have no control over the direction where XML
>industry is heading, but you are one of the people who decides that
>direction, aren't you.

I help design technologies and present them to the market. The market then 
decides if these technologies are useful. The XML industry is not a flock 
of sheep that blindly follow anybody with a Powerpoint presentation.

I've had more influence on some Working Groups than on others. Although I 
have been a member of the XML Schema Working Group from the beginning, I 
would have designed a schema language rather differently. XML Schema is not 
my brainchild. When it first came out, I was extremely concerned. I've been 
using it a lot lately, and I do find it quite useful.

>I suppose people in the industry trust W3C (or IOW you) to guide them.
>They trust that a spec with W3C's name is a good one. This trust is not
>something anyone can take easily.

Caveat Emptor.

Any standards body has good standards and bad standards. The market decides 
which standards to adopt. I think the W3C has a good enough track record 
that putting the W3C name on a spec lends it some credibility, but there 
are certainly some W3C specs that I find useless, overly complex, or badly 

My take on XML Schema is that it is useful, overly complex but not fatally 
so, and designed in a klutzy but usable manner. On balance, the market 
seems to be adopting it, and there are no overwhelming reasons to fight it. 
It is useful, and it will be used.



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