OnlineRePair: A Recompressor for XML Structures

Summary form only given. Grammar-based compression yields high compression ratios for XML document trees. However, the holy grail of grammar-based compression has been how to support incremental updates. Supporting updates is a crucial demand for many applications. The best available method decompresses the grammar, performs the update, and compresses the result. The new Online Repair algorithm presented here recompresses a given updated tree grammar directly, without decompression. Surprisingly, the algorithm yields the same compression ratios as the decompress-update-compress strategy, while being much more efficient in time and space.