Introducing AppleScript Libraries

In a major update and enhancement to its native scripting language, OS X delivers a new plugin architecture for AppleScript, enabling easy development and access to custom sets of functions and methods. Each individual AppleScript Library, saved as an AppleScript script file, can publish its own scripting terminology, and contain dozens of routines written in native AppleScript or the incredibly powerful AppleScriptObjective-C. Scripting just got a whole lot better!

WWDC 2013 - Session 416 - macOS