Shotwell Pluggable Interface Technology (SPIT)
This is the front-end interface for all modules (i.e. .so/.la files) that allows for Shotwell to query them for information and to get a list of all plug-ins stored in the module. This is named Shotwell Pluggable Interface Technology (SPIT). This is intended only to last long enough for another generic plug-in library (most likely Peas) to be used later.
The Spit namespace is used for all interfaces and code that are made available to plugins or are exposed by plugins.
More information can be found at http://trac.yorba.org/wiki/ShotwellArchWritingPlugins