- Add something of a 'history list of bound goals', through the arachne
  engine. Then, put a limit on the amount of times some goal occurs: the
  goal selection might ignore that goal then, for further selection.
- Maybe it helps to fix the agents of the claim run (i.e. all different
  agents?, this restricts the attacks somewhat), make a switch for this.
- SConstruct file should check whether ctags actually exists (avoiding
  errors)
- Proof output should be XML, with an external converter to dot format.
- States XML output, with limiter (for explanations/analysis)
- Internal hash over input files (maybe after parsing?) and switch
  structure. This would make a caching mechanism much easier.