Thanks you! Yep, multi-word idioms are tough. How do you quantify whether a phrase is just a "sum" of it's words, or is there some additional meaning, "idiomness" to it. I haven't thought a lot about that yet, but it's a problem that I need to solve for this.
If you’d like to discuss these issues, feel free to get in touch. My website URL is on my profile page. I’m not a programmer or expert on natural language processing, but I have worked on over a dozen Japanese-English and English-Japanese dictionaries and enjoy thinking about such problems.
