Modular Design Patterns

I've started drawing plugs in Java, like connectors using bezier curves, but just the visual stuff.

Then I begin wondering about making some kind of modular thing, with inputs and outputs. However, I'm very confused on decisions about how to implement it. Let's say for example, a modular synthesizer, or Pure Data / MaxMSP concepts, in which you have modules, and any module has attributes, inputs and ouputs.

I wonder if you know what keywords should I use to search something to read about. I need some basic examples or abstract ideas concerning this kind of interface. Which design patterns should I use and how.