illegal namespace usage

[David Megginson]

Simon St.Laurent writes:

 > Basically, none of these applications is really doing anything
 > exciting that couldn't have been done just by focusing on the
 > prefix.  While (hopefully) they do check beyond the prefix, none of
 > them has explored the terra incognita that's out there.

That's not quite true.  While it is true that certain XML features,
like attribute default values and DTD-based validation, tend to grind
gears a bit with Namespaces, there is a big advantage over simple
prefix matching because prefixes cannot be guaranteed unique, and
Namespace URIs can.  This matters an awful lot for blind data
exchange.

To give a simple example, consider HTML browsers.  Let's say that we
didn't have Namespaces, but we all agreed that basic HTML elements and 
attributes had unprefixed names.  Most people would probably concede
the prefix 'ms:' to Microsoft and the prefix 'ns:' to Netscape (and
maybe also 'mz:'), so there wouldn't be any risk of collision there.

What about the rest of the world, though, especially the smaller
vendors?  I'm probably safe taking the prefix 'megg:' for my HTML
extensions (just as I didn't have to pay anyone on e-bay for
megginson.com), but are you sure that there is only one vendor or
document-type designer in the whole world who will want to use the
prefix 'real:', or 'news:'?  Without Namespaces, you end up having to
set up a prefix registry, and it gets silly fast (people will compete
for good prefixes like they compete for domain names).


All the best,


David

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

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