290 Chapter 7 Clustering
For non-transaction data, patterns X and Y are conjunctions of (attribute =
value) equalities. For example, (no.-in-household = 4) ∧ (household-income =
$50,000) ⇒ (no.-of-cars = 2) is an association rule with respect to the non-
transaction data. The rule implies that if the number of family members in
a household is four and the entire household income is $50,000, then it is
highly likely that the number of cars in the family is 2.
Since the number of specific attribute values for these non-transaction
data may be hundreds or even thousands, there can be an exponential num-
ber of rules to be examined. Clustering rules that are similar and adjacent can
significantly reduce the overall number of association rules ...