Differentially Encoded Search Trees

Let X = x₁, x₂,.... x_n be a sequence of non-decreasing integer values. Storing a compressed representation of X that supports access and search is a problem that occurs in many domains. The most common solution to this problem encodes the differences between consecutive elements in the sequence, and includes additional information (samples) to support efficient searching on the encoded values. We introduce a completely different alternative that achieves compression by encoding the differences in a search tree. Our proposal has many applications such as the representation of posting lists, geographic data, sparse bitmaps, and compressed suffix arrays, to name just a few. The structure is practical and we provide an experimental comparison to show that it is also competitive with the existing techniques.