What is the "BACK BONE" of Business Process Management?

The back bone of BPM is the process flow diagram. This flow is drawn using

Business Process Model and Notation (BPMN) which is a graphical representation for specifying business processes in a business process model.

In this process flow you put a diagram for your business process.

This also allows for a simulation of the process to allow improvement and testing and facilitate the automation of your process

ERP - Entreprise Resource Planning is the Backbone of Business Process Management(BPM). As ERP is the only mechanism to control the Procedures and Policies developed through BPM

To me Backbone of BPM is its maturity check and analysis phase.

Backbone of business process is Business Rules, KPI & CSF; without which BPM is not complete.

To me back bone of BPM is Maturity model & Governance of BPM.