xml-dev - Re: ATTN: Please comment on XHTML (before it's too late)

[David Megginson <david@megginson.com>]

Paul Prescod writes:

 > How can you know, in 1999, whether Internet Explorer 5.0 will work with
 > HTML 6 documents? You cannot. If robust behavior is your primary goal
 > then you must presume not. 

I agree that there needs to be some sort of versioning available -- it
could be an html:version attribute (the best solution, I think), or
perhaps just the version of the DTD used in the DOCTYPE declaration
(much messier).  

I think that Namespaces are the wrong tool to use for versioning,
because using them that way makes easy, typical jobs much harder, and
that's just bad design.

 > > If you don't believe that versioning is a problem on
 > >    the Web, then look at the lack of even Java 1.1 applets for general
 > >    use (because Netscape 3.0 doesn't have a Java 1.1 VM).
 > 
 > What would you have JavaSoft do? Pretend that Java 1.1 programs are
 > really Java 1.0 programs so that the crash occurs deep in the JVM
 > instead of at the point that the problem is first detected? "Hmmm. It's
 > looking for a method I don't have. I'll just return NULL and hope it
 > works."

Fortunately, XML isn't source code (or compiled code), so we don't
have the same problem -- I was using that example only to demonstrate
that once there's software deployed that recognizes a certain set of
XHTML Namespaces (preferably a set with one member), it will be very
difficult to introduce any new Namespaces.

 > No version 1.x software can magically handle version 2.x data without a
 > well-defined graceful degradation mechanism. You are asking the XHTML
 > people to pretend that they have that mechanism when they do not.

They already have the mechanism: if you see an unknown attribute,
ignore it; if you see an unknown element, ignore its start and end
tags and process the content.  It's not elegant, but it's workable.

That said, as I mentioned above, I agree that some sort of versioning
is needed -- the three-Namespace approach just seems equivalent to
amputating my leg to get rid of a wart.


All the best,


David

-- 
David Megginson                 david@megginson.com
           http://www.megginson.com/

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