Browsing by Author "Hoffmann, Benjamin Sascha"

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    Similarity search with set intersection as a distance measure
    (2010) Hoffmann, Benjamin Sascha; Diekert, Volker (Prof. Dr.)
    This thesis deals with a fundamental algorithmic problem. Given a database of sets and a query set, we want to determine a set from the database that has a maximal intersection with the query set. It is allowed to preprocess the database so that queries can be answered efficiently. We solve the approximate version of this problem. We investigate two randomized input models which are derived from real inputs. We present a deterministic algorithm for each of them. Under the assumption that the database and the query set follow one of these models, the corresponding algorithm determines with high probability a set from the database that has no maximal intersection with the query set, but an intersection that achieves a large proportion of the maximal size. Depending on the model, the query time is either quasi-linear in the sum of the database size and the number of different elements from all sets, or it is polylogarithmic in the database size. Thus, both algorithms are significantly faster than a naive algorithm intersecting the query set with each single database set.