By "consumer," I mean a class/system that calls or uses another through its interface or API. What's the name for the other class/system, the one that gets called?
In a network context, a consumer is called a "client" and its counterpart is a "server", but I'm looking for a term that doesn't necessarily involve a network.
I thought the right word was "producer", but Martin Fowler calls it a "supplier" in some articles (like this one). Can anyone point to an authoritative source that defines this?