Compressed Representation of Dynamic Binary Relations with Applications

Abstract: We introduce a dynamic data structure for the compact representation of binary relations $\mathcal{R} \subseteq A \times B$. The data structure is a dynamic variant of the k$^2$-tree, a static compact representation that takes advantage of clustering in the binary relation to achieve compression. Our structure can efficiently check whether two objects $(a,b) \in A \times B$ are related, and list the objects of $B$ related to some $a \in A$ and vice versa. Additionally, our structure allows inserting and deleting pairs $(a,b)$ in the relation, as well as modifying the base sets $A$ and $B$. We test our dynamic data structure in different contexts, including the representation of Web graphs and RDF databases. Our experiments show that our dynamic data structure achieves good compression ratios and fast query times, close to those of a static representation, while also providing efficient support for updates in the represented binary relation.