For what it's worth, I think that an embedded DSL to represent most expressions tersely is a worthwhile idea to explore—it's just a more expensive one. That's a cost-effective choice at a some levels of resourcing, but not every level of resourcing.

Also, the IRS open source Direct File and their Fact Graph too. https://news.ycombinator.com/item?id=45599567 https://news.ycombinator.com/item?id=44131901 https://github.com/IRS-Public/direct-file/blob/main/direct-f...

The graph is xml.