Compact Binary Relation Representations with Rich Functionality by Jérémy Barbay, Francisco Claude, Gonzalo Navarro.
Binary relations are an important abstraction arising in many data representation problems. The data structures proposed so far to represent them support just a few basic operations required to fit one particular application. We identify many of those operations arising in applications and generalize them into a wide set of desirable queries for a binary relation representation. We also identify reductions among those operations. We then introduce several novel binary relation representations, some simple and some quite sophisticated, that not only are space-efficient but also efficiently support a large subset of the desired queries.
Read the introduction (runs about two of the thirty-two pages) and tell me you aren’t interested. Go ahead.
Just the start of what looks like a very interesting line of research.