Throwaway, used to work at the NLU unit of Alexa about 5 years ago. There is some ML going on but as with all ML projects I have worked on people want control. This means you add rules for the "important" stuff. You also add test cases to make sure the ML works. But if you already have those test cases, why not just match on them directly? There are also advanced techniques for generating examples (FST for example).
What this culminated in is a platform where 80% of request, and pretty much 99% of "commands" are served by rules built with a team of linguists.
What this culminated in is a platform where 80% of request, and pretty much 99% of "commands" are served by rules built with a team of linguists.