A quick skim of the article suggests it's a study of the implications of allowing query planning in programs which are notionally finite but may have unbounded computation. Interesting.

https://codeberg.org/veqq/declarative-dsls is built around a query language working on tables/dataframes, hashmaps, arrays, strings etc. in the same way. I ended up allowing things like :where :group-by etc. in `select` go in any order and then allowing you to use ->> macros to micromanage the execution order.