Re: RDDL: new natures

[Elliotte Harold <elharo@metalab.unc.edu>]

Jonathan Borden wrote:

> A class has a (i.e. one) set or group of members. If a namespace URI 
> identifies a class then what is the set of members:
> 
> a) the set of names in the namespace (for example)
> b) the set of documents that validate to a given schema (for example)

I don't buy it. First of all I don't think a namespace URI identifies 
the set of names in a namespace. That's simply not how namespace URIs 
are used. I've heard people assert that principle, but attempting to 
follow that idea leads them down a maze of twisty little passages, all 
different.

In an XML document, a namespace URI identifies a local name as belonging 
to a particular namespace. That's a subtly different thing, but the 
difference is important. There is no one unique, fixed set of names in a 
namespace to be identified; and working from the assumption that there 
is leads to brittle software.

Secondly, I don't think it matters if we use the namespace URI in 
clearly different contexts for different results. A URI in an xmlns 
attribute means one thing. The same URI typed into a browser's location 
bar means something else. And the same URI in a rddl:resource attribute 
is something else still. This bothers me not at all. I see no ambiguity 
or confusion. In fact, quite the opposite. Using the same strings in 
these different contexts indicates that there is a connection between them.

-- 
Elliotte Rusty Harold  elharo@metalab.unc.edu
Java I/O 2nd Edition Just Published!
http://www.cafeaulait.org/books/javaio2/
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