I had to double-check that, knowing CDuce as an XML-oriented language from when XML was hip around almost twenty years ago - and indeed it's that language for manipulating XML. It's been a while but I thought the point was to experiment with static typing of XML transformations, but ultimately type inference complexity results hit a wall and weren't convincing from a practical PoV. But what do I know - after all, adding types on top of a language that isn't statically typed seems like a pointless exercise to me when there are plenty statically typed languages. I guess it might make sense for a Python code base that's gotten out of control maybe?