The ALSA scenario or use case manager is a LGPL library designed to allow high level control of audio scenarios or use cases in sound device hardware. It is intended to be used by applications to change the hardware audio scenario of a device in a generic and portable manner. e.g. a dialer application may want to set a "GSM phone call" scenario or a media player may want to set a "playback via headphones" scenario.
This library is not meant to replace gstreamer, PulseAudio or a sound server, but is meant to work in tandem with such audio software.
The library is still work in progress. More info can be found here atm.