[jimbokun]

Sometimes.

Sometimes it is one or more programs writing to a queue or topic, and other programs reading from that topic.

Or programs writing to and others reading from a Unix pipe.

Or programs talking to each other using HTTP.

Or Erlang processes communicating concurrently on one machine or across a network.

Or different programs sharing one database.

Or many objects communicating by passing messages in a small talk program.

There are many ways to encapsulate programs and have them interact.

[wduquette]

Or to put it another way…clean architecture is how you arrange the code so that you don’t need to keep ALL of it in your head at once, just the big picture and this bit here.

[ellis0n]

Totally agree and it depends on the current context of the programmer. For example, in the ACPUL language the program is split into boot images, files, modules, functions and expressions. All of these represent different levels of context encapsulation

[minkles]

> Or programs writing to and others reading from a Unix pipe.

write(message), read() -> message

> Or programs talking to each other using HTTP.

request() -> response

> Or Erlang processes communicating concurrently on one machine or across a network.

sendMess(message), waitMess() -> message

> Or different programs sharing one database.

execute(query) -> response

...

I'm a mathematician at heart so I'm staying away from category theory as long as possible.