# Narrow waist

[Source](https://www.oilshell.org/cross-ref.html?tag=narrow-waist#narrow-waist)
The narrow waist (of an hourglass) is a software concept that solves an interoperability problem, avoiding an O(M × N) explosion. All of these are narrow waists:

-   Interchange [[format]]s like [[JSON]]
-   Networking [[protocol]]s like [[HTTP]]
-   Operating system interfaces like [[Win32]] and [[POSIX]]
-   Instruction set architectures like [[x86]], and arguably [[WebAssembly]].