Fuzzy sets and fuzzy logic research aims to bridge the gap between the cris
p world of math and the real world. Fuzzy set theory was applied to many di
fferent areas, from control to databases. Sometimes the number of events in
an event-driven system may become very high and unmanageable. Therefore, i
t is very useful to organize the events into fuzzy event sets also introduc
ing the benefits of the fuzzy set theory, All the events that have occurred
in a system can be stored in event histories which contain precious hidden
information, In this paper, we propose a method for automated construction
of fuzzy event sets out of event histories via data mining techniques. The
useful information hidden in the event history is extracted into a matrix
called sequential proximity matrix. This matrix shows the proximities of ev
ents and it is used for fuzzy rule execution via similarity based event det
ection and construction of fuzzy event sets. Our application platform is ac
tive databases. We describe how fuzzy event sets can be exploited for simil
arity based event detection and fuzzy rule execution in active database sys
tems.