have a fitness of 1, or perfect fitness,
with respect to the event log. Model
M2 has a fitness 0.8 for the event log
consisting of 1,391 cases. Intuitively,
this means 80% of the events in the
log are explained by the model. Our
experience with conformance check-
ing in dozens of organizations shows
real-life processes often deviate from
the simplified Visio or PowerPoint
representations traditionally used by
process analysts.

Model Enhancement
A process model can be extended or
improved through alignment between
event log and model, and a non-fit-
ting process model can be corrected
through the diagnostics provided by
the alignment. If the alignment con-
tains many (e, ) moves, it might make
sense to allow for skipping activity e in
the model. Moreover, event logs may
contain information about resources,

Figure 2. An event log and four potential process models—M1, M2, M3, and M4—aiming to describe observed behavior.

M1

b
examine
thoroughly
a
start register
request
c
examine
casually
decide
e
pay
compensation
g
end
event log
acdeh
abdeg
adceh
abdeh
acdeg
adceg
adbeh
acdefdbeh
adbeg
acdefbdeh
acdefbdeg
acdefdbeg
adcefcdeh
adcefdbeh
adcefbdeg
acdefbdefdbeg
adcefdbeg
adcefbdefbdeg
adcefdbefbdeh
adbefbdefdbeg
adcefdbefcdefdbeg
455

d
check ticket
reject
request
h
reinitiate
request
f
M2

a
start register
request
c
examine
casually
d
check
ticket
decide
e
reject
request
h
end
M3

b examine thoroughly
d check ticket
pay
compensation
g
a
start register
request
examine
casually
c
decide e
end
reinitiate
request f
reject
request
h
M4

start
a
register
request
a
register
request
a
a
register
request
register
request
c
examine
casually
d
check
ticket
c
examine
casually
d
check
ticket
…
d
check
ticket
examine
casually
c
d
check
ticket
examine
casually
c
decide
e
decide
e
decide
e
decide
e
reject
request
h
end
reject
request
h
g
g
pay
compensation
pay
compensation
(all 21 variants seen in the log)

a
register
request
a
register
request
a
register
request
b
d
check
ticket
b
examine
thoroughly
examine
thoroughly
d
check
ticket
b
d
check
ticket
examine
thoroughly
decide
e
decide
e
decide
e
reject
request
h
reject
request
h
g
pay
compensation
AuguST2012 | vOL. 55 | NO. 8 | CoMMuniCAtionS oF thE ACM 79