The process trace of a process captures the sequence
of states traversed by the process from initialization to termination.
Formally, it is denoted by P or 
, and is exactly the
same as the timed process trace without the field named time.
A program trace, 
, of a trace E
is a tuple of the process traces of
each of the processes in that trace.
Formally, 
, where N is the total number of
processes in trace E, and 
is the
process trace of process n (where 
).
If two traces have the same program trace, they are
equivalent traces.
The program trace set,
, of program P for input I, is the set of all
possible program traces of the program
for the given input i.e. 
.
P is a deterministic program
if for every
input I, 
contains only one program trace.
It is easy to see that all sequential programs
are deterministic.