  We implement the semantics of server operations using parameterised lenses.
They allow us to define endpoints and extend them using classical lens
composition. The parameterised nature of lenses models state updates while the
lens laws mimic properties expected from HTTP.
  This first approach to server development is extended to use dependent
parameterised lenses. An upgrade necessary to model not only endpoints, but
entire servers, unlocking the ability to compose them together.
