I am curious to see where async would fit. I recognize distributed async is beyond scope for Rex. Given the treatment of content addressable storage (CAS), one could specify workflow states declaratively, poll artifacts for next, and fire tasks to a delegate and then move forward. It would be nice to have a subsystem do that. A question is where parallelism is useful in your scientific workflows, and where it blocks. Quantum chemistry use cases (QDX is behind Rex) are presently beyond me, so I have no idea.

I am thinking that Rex programs are inteneded as an output from a higher level worklow specification language. It would be interesting to see that.

Great work! Will be curious to see how it competes with the existing workflow languages such as Nextflow or Snakemake - do you by any chance have a "Why migrate from Nextflow/Snakemake to Rex" pitch I could read somewhere?

I expected a reference to Dex, but they seem to be unrelated?

https://github.com/google-research/dex-lang

Presumably, not to be confused with Rexx[1]. Namespace collisions ... or perhaps "wrecks".

1. https://en.wikipedia.org/wiki/Rexx.