Let $\mathcal{S}$ be a collection of sets. A set straight-line program that enumerates $\mathcal{S}$ is a sequence of sets $B_1,\ldots,B_m$, such that
- $\mathcal{S}\subseteq \{B_1,\ldots,B_m\}$.
- For each $i$, either $|B_i|=1$ or $B_i = B_j\cup B_k$ for some $j,k<i$.
Have this kind of problem been studied before?