TT) the usual
  relationship of initiator/responder may be reversed.
  In some cases a given implementation may be used for multiple Things
  and a single Thing may also act as both client and server on
  multiple interfaces.
</p>
<p>
  We only count systems with mostly independent code bases
  as distinct implementations.
  There are however some cases (documented in the following) where
  implementations shared components but were still considered substantially
  independent implementations.  In cases whe