https://arxiv.org/pdf/1908.05156.pdf
NB: I read this over the weekend and am probably confused on some of the points, but I wanted to get what I did retain down before I forgot.
Aleph is a fully asyncronous multimode protocol for building a blockchain-style over a DAG of “units”.
A unit is a list of parent signatures, a list of transactions, and some other metadata. A unit must point to other units from other nodes that are in prior rounds. This is the DAG, pointing back to some genesis unit. Once a unit is produced, it is broadcast using RBC over all units.