Refactoring Traits and Policies (in Containers)

[Milburn Young]

I see the STL using class templates accepting a traits and a policy.
To me, the traits are the "what" and the policy is the "how". How can
a policy know what to do without the traits of the topic? Wouldn't it
be better for containers to take a policy template argument and for
the policy to take a traits template argument? Consider an allocator
(policy) that is going to be used in a multi-threaded environment.
The programmer could use something like the following (simplified)
traits.

template<typena me TYPE>
struct NormalTraits
{
typedef TYPE value_type;
typedef value_type *pointer;
typedef std::size_t size_type;
};
template<>
struct NormalTraits<vo id>
{
private: typedef void TYPE;
typedef TYPE value_type;
typedef value_type *pointer;
typedef std::size_t size_type;
};

template<typena me TYPE>
struct VolatileTraits
{
typedef TYPE value_type;
typedef volatile value_type *pointer;
typedef std::size_t size_type;
};
template<>
struct VolatileTraits< void>
{
private: typedef void TYPE;
typedef TYPE value_type;
typedef volatile value_type *pointer;
typedef std::size_t size_type;
};

Now, a programmer could specify the VolatileTraits< to an allocator
policy for a multi-threaded container and the policy would know what
types should be given to the signatures of methods like 'pointer
allocate( size_type, typename
TRAITS::rebind< void>::other::c onst_pointer )'. How are traits
reflected in policies if they are only introduced to the container?
When would my refactoring not work?

Milburn Young