Garofolo's central definition of what makes something a service. Autonomy requirements: (1) no one asks a service for anything — a GET API behind HTTP is just a database; (2) the service asks no one else for anything, otherwise it has dependencies and isn't autonomous; (3) the service is completely oblivious to the rest of the system, and the rest is oblivious to it. Consequence: a service can go down without taking others with it — the system just does less.