%T Exception Handling and Checkpointing in CSP
%A  Mads Ohm Larsen,  Brian Vinter
%E Peter H. Welch,  Frederick R. M. Barnes,  Kevin Chalmers,  Jan Bækgaard Pedersen,  Adam T. Sampson
%B Communicating Process Architectures 2012
%X This paper describes work in progress. It presents a new way
   of looking
at some of the basics of CSP. The primary
   contributions is exception
handling and checkpointing of
   processes and the ability to roll back to
a known
   checkpoint.  Channels are discussed as communication
   events
which is monitored by a supervisor process.  The
   supervisor process is
also used to formalise poison and
   retire events.  Exception handling and
checkpointing are
   used as means of recovering from an catastrophe. 
   The
supervisor process is central to checkpointing and
   recovery as well.
Three different kind of exception handling
   is discussed: fail\-stop,
retire\-like fail\-stop, and check
   pointing.  Fail\-stop works like poison,
and retire\-like
   fail\-stop works like retire.  Checkpointing works
   by
telling the supervisor process to roll back both
   participants in a
communication event, to a state
   immediately after their last successful
communication. Only
   fail\-stop exceptions have been implemented in PyCSP
to this
   point.