I. BPMN

It was a longtime when BPM vendors have no consensus. There were some standards and specifications but none of them can gather enough traction to become an global standard for doing BPM. Then, BPM vendors together create a standard that unifies the BPM landscape called BPMN, which stands for 'Business Process Model and Notation'.

BPMN 1.x focused on graphical notation only. It defines how concepts such as a human task, an executable script, automated decisions… are visualized in a vendor-neutral standardized way.

This is a simple process diagram in BPMN:

Business users and developers can understand business activities’ flow and process easily with 4 basic element categories including set of graphical elements.

• Flow objects: events, activities, gateways.
• Connecting objects: sequence flow, message flow, association.
• Swim lanes: pool, lane.
• Artifacts: data object, group, annotation.

For details, please visit: BPMN Quick Guide.

BPMN 2.0 extends BPMN 1.x with execution semantics and a common exchange format. Now definition models are not only exchangeable between graphical editors but also be executed as-is on any BPMN 2.0 compliant engine such as Activiti.

II. Activiti

1. Overview

Activiti is a BPM engine with core goal: - take a process definition including human tasks, service calls, then execute them in a certain order. - expose API to start, manage and query data about process instances for that definition.

More at:

https://grokonez.com/java-integration/introduction-activity-java-bpm-engine

How to quick start Activiti – a Java BPM Engine with SpringBoot