Given a set of transactions D, the problem of mining association rules is to generate all association
rules that have support and condence greater than the user-specied minimum support
(called minsup) and minimum condence (called minconf ) respectively. Our discussion is neutral
with respect to the representation of D. For example, D could be a data le, a relational table, or
the result of a relational expression.
An algorithm for nding all association rules, henceforth referred to as the AIS algorithm, was
presented in [AIS93b]. Another algorithm for this task, called the SETM algorithm, has been
proposed in [HS93]. In this paper, we present two new algorithms, Apriori and AprioriTid, that
dier fundamentally from these algorithms. We present experimental results, using both synthetic
and real-life data, showing that the proposed algorithms always outperform the earlier algorithms.
The performance gap is shown to increase with problem size, and ranges from a factor of three
for small problems to more than an order of magnitude for large problems. We then discuss
how the best features of Apriori and AprioriTid can be combined into a hybrid algorithm, called
AprioriHybrid. Experiments show that the AprioriHybrid has excellent scale-up properties, opening
up the feasibility of mining association rules over very large databases.