RNS artifacts is a library for smart contract development.
Source: github.com/rnsdomains/rns-artifacts
It provides implementations of RNS Registry, Registrars, and Resolvers which you can deploy as-is or extend to suit your needs, as well as Solidity components to build custom contracts and more complex decentralized systems.
Resolver: contract responsible for performing resource lookups for a name - for instance, returning a contract address, a content hash, or IP address(es) as appropriate.