1. Introduction  
2. Data Representations for Irregularly Sampled Time Series  
3. Inference Tasks  
4. Modeling Primitives for Irregularly Sampled Time Series  
5. Discretization-Based Approaches  
6. Interpolation-Based Approaches  
7. Recurrence-Based Approaches  
8. Attention-Based Approaches  
9. Structural Invariance-Based Approaches  
10. Predictive Performance  
11. Discussion and Directions for Future Work  