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
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
