Entities and their relations are the backbone of many Ruby applications â€“ from trivial, one-off commandline utilities to full-blown social network websites. The good old relational databases, while showing extreme abilities in both adaptation and survival, are no longer the obvious choice for persistence â€“ and sometimes obviously not an ideal one. This talk discusses various entity/relation modelling approaches and different persistence techniques â€“ from rigid schemas in suits to collections of hippie free-form documents; from good old (transactional!) PStore through join-table-happy RDBMSes and muscle-flexing NoSQL hools to (social!) graph databases, waiting patiently for broader recognition and prime time. Quite a few interesting Ruby libraries for gluing all this together are also pondered upon â€“ from world-class champions like Active Record or ARel to less known gems like Candy and Ambition.