Reactive Relational Algebra

Personally, relational algebra feels more "invented" than "discovered". Sometimes the whole thing smells like a kludge that weasled its way into modern CS curricula.

But hey, if you're rigorously thinking about databases/tables/spreadsheets, and you need to build on the work of really really smart people, then relational algebra starts looking like an attractive corner of math & computing theory.

Anyway, so here I am, trying to build "better spreadsheets", and I'm playing with "derived" tables that feel like database views:

The whole reason I added the wibbly wobbly timey wimey stuff is that my spreadsheet program works with async data (e.g. HTTP requests, SQL queries).

I somehow settled on a time-indexed paradigm inspired by discrete functional reactive programming. My brain is apparently too smooth to grok what FRP is, so I have no clue if my idea here is actually related or not.

But anyway, when I started building actual async spreadsheets, I found myself making lots of intermediate tables to emulate "memory". At some point, I realized it was easiest to "merge" tables using self-reference:

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