NSAccessibility — Mac OS X 10.2
Cocoa provides support for accessibility, which gives Cocoa applications the ability to work with other assistive applications, such as screen readers. This informal protocol declares the methods that classes in an application must implement to interface with the accessibility system. The great majority of Application Kit classes implement this protocol, meaning that Cocoa applications are largely accessible to assistive technologies. However, if you do a great deal of customization to existing Cocoa classes, it may be necessary to implement portions of the protocol yourself.