Abstract

Abstract. A simple linear-time algorithm for constructing a linear context-free tree grammar of size O(rg + rg log(n/rg)) for a given input tree T of size n is presented, where g is the size of a minimal linear context-free tree grammar for T, and r is the maximal rank of symbols in T (which is a constant in many applications). This is the first example of a grammar-based tree compression algorithm with a good approximation ratio. The analysis of the algorithm uses an extension of the recompression technique (used in the context of grammar-based string compression) from strings to trees. 1.