What are “sums-and-products” data structures?

Question

A recent blog post on William Cook\'s Fusings mentions:

The key point is that structures in Ensō are viewed holistically as graphs, not as individual

Answer 1

From the lecture notes for the Coursera course, "Programming Languages", offered by Univ. of Washington:

"Why product and sum? It is related to the fact that in Boolean algebra where 0 is false and 1 is true, and works like multiply and or works like addition."