Databases of sequences can contain consecutive repetitions of items. This is the case in particular when some items represent
discretized quantitative values. We show that on such databases, a typical algorithm like the SPADE algorithm tends to loose
its efficiency. SPADE is based on the used of lists containing the localization of the occurrences of a pattern in the sequences
and these lists are not appropriated in the case of data with repetitions. We introduce the concept of generalized occurrences and the corresponding primitive operators to manipulate them. We present an algorithm called GO-SPADE that extends SPADE
to incorporate generalized occurrences. Finally we present experiments showing that GO-SPADE can handle sequences containing
consecutive repetitions at nearly no extra cost.
Keywords frequent sequential pattern mining - generalized occurrences - SPADE