Policy information in computer networking today, such as reachability objectives of a controller program running on a Software Defined Network (henceforth referred to as SDN) or Border Gateway Protocol (henceforth referred to as BGP) configurations independently set by autonomous networks, are hard to manage. This is in sharp contrast to the relational data structured in a database that allows easy access. This paper asks why cannot (or how can) we turn network policies into relational data. One difficulty to such an approach is that a policy does not always translate to a definite network snapshot, but rather is fully described only when we include all the possible network states it admits. We propose relational policies that, while capable of representing and manipulating sets of network states in exactly the same way as a single one, form a strong representation system and accurately capture the information in a policy with the usual Structured Query Language (henceforth referred to as SQL) interface. We demonstrate how, like relational database improves application productivity and enables rapid innovation, relational policies allow us to extend the elegant solutions that the database community developed, to mediate multiple data sources in order to address long-standing challenges and new opportunities for autonomous policy making in the distributed networking environment.We also show the feasibility of relational policies by evaluation on synthetic policies and realistic network topologies.
