Joe Armstrong: Grow software apps by adding small communicating objects

We should grow things (software applications) by adding more small communicating objects, rather than making larger and larger non-communicating objects.

Concentrating on the communication provides a higher level of abstraction than concentrating on the function APIs used within the system. Black-box equivalence says that two systems are equivalent if they cannot be distinguished by observing their communication patterns. Two black-boxes are equivalent if they have identical input/output behavior.

When we connect black boxes together we don't care what programming languages have been used inside the black boxes, we don't care how the code inside the black boxes has been organized, we just have to obey the communication protocols.

Erlang programs are the exception. Erlang programs are intentionally structured as communicating processes — they are the ultimate micro-services.

Large Erlang applications have a flat “bus like” structure. They are structured as independent parallel applications hanging off a common communication bus. This leads to architectures that are easy to understand and debug and collaborations which are easy to program.

~ From this post by Joe Armstrong, author of the book Programming Erlang: Software for a Concurrent World