Comparing Recurring Lexico-Syntactic Trees (RLTs) and Ngram Techniques for Extended Phraseology Extraction

This paper aims at assessing to what extent a syntax-based method (Recurring Lexicosyntactic Trees (RLT) extraction) allows us to extract large phraseological units such as prefabricated routines, e.g. as previously said or as far as we/I know in scientific writing. In order to evaluate this method, we compare it to the classical ngram extraction technique, on a subset of recurring segments including speech verbs in a French corpus of scientific writing. Results show that the RLT extraction technique is far more accurate for extended MWEs such as routines or collocations but performs more poorly for surface phenomena such as syntactic constructions or fully frozen expressions.