  To understand and explain process behaviour we need to be able to see it, and
decide its significance, i.e. be able to tell a story about its behaviours.
This paper describes a few of the modelling challenges that underlie monitoring
and observation of processes in IT, by human or by software. The topic of the
observability of systems has been elevated recently in connection with computer
monitoring and tracing of processes for debugging and forensics. It raises the
issue of well-known principles of measurement, in bounded contexts, but these
issues have been left implicit in the Computer Science literature. This paper
aims to remedy this omission, by laying out a simple promise theoretic model,
summarizing a long standing trail of work on the observation of distributed
systems, based on elementary distinguishability of observations, and classical
causality, with history. Three distinct views of a system are sought, across a
number of scales, that described how information is transmitted (and lost) as
it moves around the system, aggregated into journals and logs.
