Question on strict conformance

[Eric Lemings]

 
Say the standard specifies:
 
namespace std {
class foo: true_type {};
};
 
Are we allowed to actually derive foo from __rw::__rw_true_type?  Or
does std::true_type and __rw::__rw_true_type only need to be
semantically equivalent to meet strict conformance?
 
Brad.