The Ferry 2.0 Table Algebra library
The table algebra  is an intermediate language used by Ferry 2.0  and DSH . It forms the input for the pathfinder  optimiser that can translate it into SQL. The library exposes a monadic interface to construct algebraic plans, it automatically performs common sub-tree elimination so that the resulting plan is as small as possible and the optimiser can do it's work better. XML rendering is present and needed for interfacing with DSH-Pathfinder, and for debugging plans with the standalone Pathfinder.