Quick technical question.

Hi all,
Does someone understand clause 1.6 of
http://www.w3.org/TR/xmlschema-1/#rcase-NameAndTypeOK ?

"R's { type definition } is validly derived given {extension } from B's
{type definition} as defined by Type Derivation OK (Complex)(5.11) or
Type Derivation OK(Simple)(5.12) as appropriate".

What does the { extension } refer to?  B's final = { extension }?  What
about final = ' ' ?

confused,
mick.