1 INTRODUCTION
2 WHAT IS EKG: HISTORY VIEW
2.1 The Brief History of EKG
2.2 The Definition of EKG
3 WHAT IS EKG: ONTOLOGY VIEW
3.1 Event Schema Induction
3.2 Script Induction
3.3 EKG Schema Induction
4 WHAT IS EKG: INSTANCE VIEW
4.1 Event Acquisition
4.2 EKG-related Representative Graphs/Systems
5 WHAT IS EKG: APPLICATION VIEW
5.1 Basic Applications
5.2 Deep Applications
6 FUTURE DIRECTIONS
6.1 High-performance Event Acquisition
6.2 Multi-modal Knowledge Processing
6.3 Interpretable EKG Research
6.4 Practical EKG Research
7 CONCLUSIONS