Document Listing for Queries with Excluded Pattern

Let D = {d1, d2, ..., dD} be a given collection of D string documents of total length n. We consider the problem of indexing D such that, whenever two patterns P and P− comes as an online query, we can list all those documents containing P but not P−. Let t represent the number of such documents. An index proposed by Fischer et al. (LATIN, 2012) can answer this query in O(|P|+ |P−|+ t+ √ n) time. However, its space requirement is O(n) bits. We propose the first linear-space index for this problem with a worst case query time of O(|P|+ |P−|+ √ n log logn+ √ nt log n).