Comment by jauntywundrkind

Really enjoyed the multi-part/multi-file tutorial for the fact-graph, a seemingly core component that I saw referenced in a couple places.

> Take a look at [Form 1040][1]. Line 12c asks the taxpayer to add lines 12a and 12b. This is a common pattern on tax forms. https://www.irs.gov/pub/irs-pdf/f1040.pdf

> There is a relationship betwen lines 12a, 12b, and 12c. In order to know what should be entered in 12c, we need to first know the values of 12a and 12b.

> This pattern might remind you of a spreadsheet. If we were to transcribe Form 1040 into Excel, we might imagine that line 12c would be a formula like =SUM(Line12A,Line12B). Excel spreadsheets are _declarative_, which is to say we define the relationships between cells using formulas, but we leave it up to Excel to determine how to solve the spreadsheet.

This is their data-relational langage.

https://github.com/IRS-Public/direct-file/blob/main/direct-f...