1 Introduction  
2 Characteristics of Dialogues  
3 Methodology  
3.1 Problem Formulation  
3.2 Dialogue Modeling Framework  
3.3 Dialogue-related Pre-training  
4 Dialogue Comprehension with Explicit Knowledge  
4.1 Auxiliary Knowledge Grounding  
4.2 Emotional Promotion  
4.3 Multilingual and Multimodal Dialogue  
5 Empirical Analysis  
5.1 Dataset  
5.2 Evaluation Metrics  
5.3 Observations  
6 Frontiers of Training Dialogue Comprehension Models  
6.1 Dialogue Disentanglement Learning  
6.2 Dialogue-aware Language Modeling  
6.3 High-quality Negative Sampling  
7 Open Challenges