Constraint: URI uniqueness

Section 2.1 defines the "Constraint: URI uniqueness" as follows:

Web architecture does not constrain a Web resource to be identified 
by a single URI.


The constraint and the title do not seem to match. Perhaps the title 
is supposed to be "URI non-uniqueness" or perhaps the text is 
supposed to be something like "Each URI identifies exactly one 
resource". However, the title suggests to me that URIs are unique, 
and the text suggests the opposite.
-- 

   Elliotte Rusty Harold
   elharo@metalab.unc.edu
   Effective XML (Addison-Wesley, 2003)
   http://www.cafeconleche.org/books/effectivexml            
   http://www.amazon.com/exec/obidos/ISBN%3D0321150406/ref%3Dnosim/cafeaulaitA