>almost everything can be modeled as a mix of source-streams + (input-data) sink-streams (output-data)
true. This is pretty much what i have been doing for 25 years and will be doing for the next like 20.
Reminds me about the time when one guy we had around read a book on finite state machines. It was, dare i say, an eye-opener for him. Since that moment until he parted with us, all what he was doing was FSAs.
But I have the feeling, that good frameworks still make some stuff easier than others, while supporting arbitrary programming/turing completeness.
For example Cycle.js, which is a structural framework for reactive programming with observables. It's made for front-end developoment, but I can also model REST and WebSocket servers with it, since almost everything can be modeled as a mix of source-streams + (input-data) sink-streams (output-data).
Since it uses observables all over the place, it makes handling these data-streams much easier an clearer, by making them first class citiziens in the app.