Re: [xml-dev] Can we treat XML elements and attributes as sets

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

Looking at that particular paragraph right now (p. 63) it doesn't seem 
precise enough. It should be clearer that it's talking about element and 
attribute names rather than element and attribute instances, though I 
suspect that can be gathered from context. That whole sentence about 
"The URIs partition the element names and attributes into disjoint sets. 
" could be deleted without losing anything.

The bit about the 1-1 relationship between namespaces and XML 
applications is also too strong. It completely misses the existence of 
numerous different XML applications that have no namespace, or that are 
in the null namespace if you prefer.

I'd used an example of genuine mathematical sets a little earlier in the 
chapter so I probably had sets on the brain when I wrote that. I'll see 
if I can clean this up in the next printing. How about this:

Namespaces distinguish between elements with different meanings but the 
same name by assigning each element a URI. Generally, all the elements 
from one XML application are assigned to one URI, and all the elements 
from a different XML application are assigned to a different URI. These 
URIs are called namespace names. Elements with the same name but 
different URIs are different kinds of elements. Elements with the same 
name and the same URI are the same kind of element. Most of the time a 
single XML application has a single namespace URI for all its elements, 
though a few applications use multiple namespaces to subdivide different 
parts of the application. For instance, XSL uses different namespaces 
for XSL Transformations (XSLT) and XSL Formatting Objects (XSL-FO).

I think that eliminates most of the pretentious pseudo-math I sometimes 
slip into.

-- 
Elliotte Rusty Harold  elharo@metalab.unc.edu
XML in a Nutshell 3rd Edition Just Published!
http://www.cafeconleche.org/books/xian3/
http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim