Scheme-OSA stands for Open Scripting Architecture. It provides an abstract interface for applications to compile, execute, and manipulate scripts without needing to know the details of the particular scripting language. Scheme-OSA bridge furnishes a Scheme user with a means of accessing the OS X multimedia and other resources from Apple and the third parties – introducing graphics, scientific plotting, dialog boxes, music, etc. into the world of Scheme language.
(via comp.lang.scheme)