calculated attribute/ namespace name

[Uwe Küssner]

hello,

a short question, i hope somebody can help.

Let's say we have a XML documents like this:

<ele xmlns:a="aa"  xmlns:b="bb"  name="foo" a:name="bar"  
b:name="foobar"  b:x="y" />

The namespace names and attributes are not known before runtime, during 
runtime of a xquery script we have two variables of type string, for 
example:
$namespace := "bb"
$attribute :="name"

here is the question: how can we extract the value of the attribute 
named $attribute with namespace name $namespace?
In the example the value of  "b:name", i.e. "foobar".

thank you very much