Beside the two parameters support and confidence additional metrics for measuring the importance of rules are provided. The following metrics are currently available:

• lift
• conviction
• long tail correlation (ltc)

Lift and conviction are standard metrics, describing the interestingness of a rule. ltc is an experimental SAT made metric, describing the capacity of a rule $X \rightarrow Y$ that a common item X refers to a rare item Y. ltc is defined as

$ltc(X \rightarrow Y) = support(X) * \log( \frac{support(X)}{support(Y)} )$

and has the following characteristics:

• ltc(X->Y) < 0: X is the rare item, pointing to a common item Y.
• ltc(X->Y) = 0: X and Y have are equal popular
• ltc(X->Y) > 0: A common item X is referring to a rare item Y.

Currently these parameters can only be activated in the configuraton file .... When activated, these values replace the 'confidence' measure as the quality criteria!