Scene Assembly Manager provides a complete workflow for using scene assembly in Maya.
Using scene assembly out of the box is very complicated and is a multi-step process, which calls for automation because it requires setting up and defining different versions of assets before they can be used efficiently.
The Maya bonus tools features the Pipe Assembly Manager (or PAM) which greatly simplifies the process of creating scene assembly representations and definitions through a simple interface.
However, the initial version of Pipe Assembly Manager had platform specific issues and lacks some practical functionality, such as the support for proxies and VRay. The current state is unknown, but since bonus tools are not supported the chance for further development is small.
Scene Assembly Manager is build upon the basic idea of how to approach the concept of scene assembly used in Pipe Assembly Manager but featuring a better and more stable workflow which is necessary for production usage.