Old and New Benchmarks for Relative Termination of String Rewrite Systems

We provide a critical assessment of the current set of benchmarks for relative SRS termination in the Termination Problems Database (TPDB): most of the benchmarks in Waldmann_19 and ICFP_10_relative are, in fact, strictly terminating (i. e., terminating when non-strict rules are considered strict), so these benchmarks should be removed, or relabelled. To fill this gap, we enumerate small relative string rewrite systems. At present, we have complete enumerations for a 2-letter alphabet up to size 11, and for a 3-letter alphabet up to size 8. For some selected benchmarks, old and new, we discuss how to prove termination, automated or not.