Discovery of frequent patterns = finding positive conjunctions that are true for a given fraction of the observations - this basic idea can be instantiated in many ways: - finding frequent sets from 0/1 data (association mining) - finding frequent episodes in sequences - finding frequent subgraphs in graphs etc. - efficient algorithms exist -- the levelwise approach - theoretical analysis of the algorithms is not trivial - leads to connections to hypergraph transversals etc. - the second part: how can the patterns be used? - sometimes interesting in themselves - can be used to approximate the joint distribution - maximum entropy approaches - combining information from several patterns - ordering patterns