[js8]

I somewhat disagree. Interestingly, one of the most extensible SW systems ever is Unix shell, which is completely opposite to the OOP idea.

The idea in Unix is that data are the interface, in case of Unix the data are unstructured text, but I think it can be generalized to systems with structured data. So contrary to OOP, most extensible systems seem to be the ones that (self)document their data structures as interface and leave it at that.

[hxegon]

Clojure agrees with this philosophy IMO. Paraphrasing, but "100 functions on 1 data structure is better than 10 functions on 10 structures"

[js8]

True. I think in general it's a philosophy of functional programming, where data structures are types, and type signature of functions are their APIs.