Declarative knowledge extraction with iterative user-defined aggregates

We present the notion of Iterative user-defined aggregates as an extension of the notion of user-defined aggregates in deductive databases. Such an extension provides a versative mechanism for defining complex aggregation functions, that are not definable as distributive aggregates. As a result, we show how such a mechanism can be applied to the specification of complex data mining tasks as user-defined aggregates. The resulting formalism provides a flexible way to customize, tune and reason on both the evaluation functions and the extracted knowledge.