Reference Capability

Definitions

In the Pony programming language, a type system feature that annotates references with capabilities (iso, val, ref, box, trn, tag) controlling what an alias can read, write, or share. Enables data-race-free concurrency by making unsafe sharing a compile-time error.
In plain English: Labels on data references that tell the compiler who is allowed to read or write the data, preventing bugs where two parts of the program fight over the same data.
Example: "Marking the buffer as iso guarantees this actor is the only one that can write to it — no locks needed."