Feuerstein et al. (2009). We regret that items 1 and 3 in Section 1.4 should be corrected to read as follows: − (Item 1) We adopt the notion of two-dimensional distributed inverted files proposed by Feuerstein et al. (2009) with the purpose of optimizing the entire system cost including computation, communication, and fixed overheads of the system. Feuerstein et al. (2009) allocated index fragments in a two-dimensional array of processors through keyword (or term) partitioning (defined in Section 2.2) and document partitioning (defined in Section 2.2). In this paper, we adopt this basic scheme with a different purpose of minimizing the average query response time by simulating collective distributed (main) memory as one integrated memory. Then, we extend this scheme so that each row of the twodimensional array stores a replicated (document-partitioned only) index shard on disk for efficient processing of multiple-keyword queries. We call this extended scheme and associated algorithms two-dimensional indexing.