Abstract

Data warehouses provide a great deal of opportunities for performing data mining tasks such as classification and clustering. Typically, updates are collected and applied to the data warehouse periodically in a batch mode, e.g., during the night. Then, all patterns derived from the warehouse by some data mining algorithm have to be updated as well. Due to the very large size of the databases, it is highly desirable to perform these updates incrementally. In this paper, we present the first incremental clustering algorithm. Our algorithm is based on the clustering algorithm DBSCAN which is applicable to any database containing data from a metric space, e.g., to a spatial database or to a WWW-log database. Due to the density-based nature of DBSCAN, the insertion or deletion of an object affects the current clustering only in the neighborhood of this object. Thus, efficient algorithms can be given for incremental insertions and deletions to an existing clustering. Based on the formal definition of clusters, it can be proven that the incremental algorithm yields the same result as DBSCAN. A performance evaluation of IncrementalDBSCAN on a spatial database as well as on a WWW-log database is presented, demonstrating the efficiency of the proposed algorithm. IncrementalDBSCAN yields significant speed-up factors over DBSCAN even for large numbers of daily updates in a data warehouse.

Citations