Indexing of Sequences of Sets for Efficient Exact and Similar Subsequence Matching

Object-relational database management systems allow users to define complex data types, such as objects, collections, and nested tables. Unfortunately, most commercially available database systems do not support either efficient querying or indexing of complex attributes. Different indexing schemes for complex data types have been proposed in the literature so far, most of them being application-oriented proposals. The lack of a single universal indexing technique for attributes containing sets and sequences of values significantly hinders practical usability of these data types in user applications. In this paper we present a novel indexing technique for sequence-valued attributes. Our index permits to index not only sequences of values, but sequences of sets of values as well. Experimental evaluation of the index proves the feasibility and benefit of the index in exact and similar matching of subsequences.