They did, and their product is great.

It is the only database/query engine that allows you to use the same SQL for both batch and streaming (with UDFs).

I have made an accessible version of a subset of Differential Dataflow (DBSP) in Python right here: https://github.com/brurucy/pydbsp

DBSP is so expressive that I have implemented a fully incremental dynamic datalog engine as a DBSP program.

Think of SQL/Datalog where the query can change in runtime, and the changes themselves (program diffs) are incrementally computed: https://github.com/brurucy/pydbsp/blob/master/notebooks/data...