The extraction of frequent patterns often yields extremely voluminous results which are difficult to handle. Computing a concise representation or cover of the frequent pattern set is thus an interesting alternative investigated by various approaches. The work presented in this article fits in such a trend. We introduce the concept of essential pattern and propose a new cover based on this concept. Such a cover makes it possible to decide whether a pattern is frequent or not, to compute its frequency and, in contrast with related work, to infer its disjunction and negation frequencies. A levelwise algorithm with a pruning step which uses the maximal frequent patterns for computing the essential patterns is proposed. Experiments show that when the number of frequent patterns is very high (strongly correlated data), the defined cover is significantly more reduced than the cover considered until now as minimal: the frequent closed patterns.
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