Comments on the formal semantics

1. Two inference rules for <attribute>?

Why do you need two inference rules for <attribute>?

2. The inference rule for <element>

What is meant by ns2?  In my understanding, if we have an element

     <foo xmlns:bar="..some url">

we have to revise the current prefix-URI mapping.  We need

ns2 = updateMapping(a, ns1)


Cheers,

Makoto