/System/Library/Frameworks/InputMethodKit.framework/Versions/A/InputMethodKit
The Input Method Kit, introduced in OS X v10.5, provides a streamlined programming interface that lets you develop input methods with far less code than older Mac programming interfaces. It is fully integrated with the Text Services Manager. The Input Method Kit allows 32-bit applications to work with 64-bit applications. The Input Method Kit provides classes and protocols for managing communication with client applications, candidates windows, and input method modes.