The division of the BAPS3 system into multiple services is an unusual aspect of its design, and is inspired primarily by UNIX philosophy. We argue for this unconventional approach as follows:
Each large chunk of functionality is clearly defined in a modular style, with defined inputs and outputs. This allows for a clean distinction between the components of the playout system.
As the services may be implemented separately, each resulting server can be swapped out at any time with a compliant alternative, with little to no disruption to the rest of the system.
If a service server crashes, the remaining aspects of the system can continue in a degraded manner until the server can be replaced. For example, if the playlist service is lost, the player can continue to play the last selected song without disruption; if the player service is lost, the playlist remains intact and can be backed up or used with a replacement player instance.
Services can be composed to form seamless pipelines of playout functionality: a player and playlist can be attached together to form a playout channel. New services can be slotted into an existing pipeline to add new functionality, and services can be combined into a single server for performance reasons.
The only service that needs to reside on the computer with sound output is (multiple instances of) the player service. Any other services can be allocated to other hardware to balance load and reuse resources.