How is Scheduler implemented in Appian?

Can you provide us with some background on what the use case is ?

We would like to build common scheduler framework to control scheduling outside of Appian rather than republish process every time scheduler config changes..

You may publish your process model as webservice and then call it based on your external scheduler. Or another option is to launch via email and that email need to be sent out by a scheduler program running outside of Appian