This problem can be addressed by adding information to the log or by using
heuristics. This can be seen as a “secondary correlation problem”, i.e., relating two
events within the same case. The primary correlation problem is to relate events
to cases, i.e., process instances [39]. Figure 4.5 shows that even within one case
there may be the need to correlate events because they belong to the same activity
instance. When implementing systems, such information can easily be added to the
logs; just provide an activity instance attribute to keep track of this. When dealing
with existing systems this is not as simple as it seems. For example, when correlating
messages between organizations there may be the need to scan the content of the
message to find a suitable identifier (e.g., address or name). It is also possible to
use heuristics to resolve most problems, e.g., in Fig. 4.5 one could just assume
a first-in-first-out order and pick the first scenario. Moreover, one may introduce
timeouts when the time between a start event and complete event is too long. For
example, start events that are not followed by a corresponding complete event within
45 minutes are removed from the log.