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   RE: Using Namespaces for Validation

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  • From: johns@syscore.com (John F. Schlesinger)
  • To: "'Sean B. Palmer'" <sean@mysterylights.com>, xml-dev@xml.org
  • Date: Thu, 19 Oct 2000 08:26:32 -0400

Sean wrote:
"...although we know that XML Schema are too complicated to use..."

I don't think XML Schema is too complicated to use, so it's not everyone.

Actually, I think it is remarkable how easy it is with XML Schema to do
things that have completely defeated products such as MQSI. Using the NEON
formatter it is not possible to nest tags, process attributes or validate
data types. With XML Schema and a validating parser (there are several that
are free and support April 7 Schema pretty well) I can validate and process
messages in a way the current message brokers can only dream of.

In my 23 years of software engineering, I have never seen a technology of
this power advance so quickly or be so well supported by both design time
and run time tools (compare with SQL for instance).

The suggestion of using the namespace as the schema location is a competitor
to XML Schema's 'hint' to the parser in xsi:schemaLocation. What parsers
will do will decide. At least your approach justifies using an http URL.

However,

Yours,
John F Schlesinger
SysCore Solutions

-----Original Message-----
From: Sean B. Palmer [mailto:sean@mysterylights.com]
Sent: Sunday, October 15, 2000 5:27 AM
To: xml-dev@xml.org
Subject: Using Namespaces for Validation


Hi Everyone,
This is a proposal for using namespaces for validation. I thought I'd send
it here because it might actalluy be *discussed* for a change...

> > If find it interesting that they used the XHTML namespace as a namespace
> > here. That may sound a bit odd, but consider: in the Modularization
> >spec. they have on at least one occasion allowed us to use DTDs as a
> > namespace. I can't help thinking "why can't we just use the DTD as a
> > namespace?"
>
> Could you elaborate, Sean?  What do you mean -- "use the DTD as a
> namespace"?

Certainly:
<html xmlns="http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
 <head>
  <title>A Simple XHTML Document</title>
 </head>
 <body>
  <p>A clean example!</p>
 </body>
</html>

As condoned by: http://www.w3.org/TR/xhtml-building/developing.html#sec_6.5.

"<html xmlns:myml="http://www.my.org/DTDs/mylanguage-1_0.dtd">"

This is a core tenet of my current work with XHTML Schemas. The DTD method
of implementation "Document Type Declaration" is out of date, and never
really caught on in the first place. This all dates back to the very first
days of the Internet when DC and Tim B-L decided to make it an application
of SGML. At first it was good idea, but as the WWW grew, it became clear
that a more extensible future was needed, and so XML came about. Then came
XML Schema as a replacement for DTD, and although we know that XML Schema
are too complicated to use, we at least have the spin-off of Namespaces to
define what namespace certain parts of the document have. I'm just saying we
should use these namespaces to *properly* define them, i.e. point them to
any form of validation document (DTD or Schema at the mo'). This means that
mixing languages becomes incredibly simple, especially when you compare it
to DTD Modularization. I know the W3C swore they wouldn't use namespaces for
validation, but I'm not a member of the W3C, and I say that using them is a
good idea, because it simplifies the WWW (like recent discussions on XHTML-L
allude to), and makes it more extensible.
Simon mentioned the XHTML 1.0 spec. even points out that using namespaces is
a good way to mix languages. So why not use them properly (or not, as the
case may be!).
If anyone bothered to read my last post [for members of this list, see
http://lists.w3.org/Archives/Public/www-talk/2000SepOct/0026.html], you
would have seen it is a tounge in cheek reply to a Dan Connolly message
of *1992*. I really think anyone interested in this conversation should read
it, even if it was only a joke!

I know I'll get flamed for using his name, but Dan Connolly was one of the
first people to suggest a means of expressing HTML as SGML: that is apparent
from the message of 1992 that I replied to. He supported SGML DTDs for many
years, but then found that no-one was using them, or supporting them for
validation. So he looked for a simpler system, and namespaces and Schemas
caught his attention. That's how I see it anyway...
The way I approach it from is that I used to be a terrible coder. When I
learned about the W3C and proper validatable HTML coding, I thought "well
why are so few people using it?", and it wasn't long before I realised that
the answer was that SGML Document Type Declarations (not definitions),
are a pain in the neck. Namespaces offer us a
way out. We even have emerging validation support in the form of XSV: but
for that you have to use xsi:schemaLocation. I'm saying just refer to it
straight with the xmlns attribute. And anyway, as long as the target
namespace
is declared in whatever schema you use (if you want to use schema), then
there
isn't a problem. That way we exploit the XML properties of XHTML.
In the future, the DTD could be replaced by a Schema, but not XML Schema, I
would suggest. I think we should consider using namespaces for validation
and extension purposes, though. This may have to be issued as an extension
to
XML 2.0, but I'm not sure about the logistics of that. At any rate, a simple
Note
from the W3C would get the ball rolling.
Final word: http://xhtml.waptechinfo.com/future/

Kindest Regards,
Sean B. Palmer
President and Founder
WAP Tech Info - http://www.waptechinfo.com/






 

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