Abstract

Sequence representations supporting not only direct access to their symbols, but also rank/select operations, are a fundamental building block in many compressed data structures. In several recent applications, the need to represent highly repetitive sequences arises, where statistical compression is ineffective. We introduce grammar-based representations for repetitive sequences, which use up to 10% of the space needed by representations based on statistical compression, and support direct access and rank/select operations within tens of microseconds.