1 Introduction  
1.1 Article Overview

2 Problem Formulation  
2.1 The Lifelong Learning Problem  
2.2 The Compositional Learning Problem

3 Categorization of Lifelong Compositional Approaches

4 Lifelong or Continual Learning  
4.1 Task-aware  
4.2 Task-agnostic  
4.3 Reusable Knowledge  
4.4 Additional Approaches

5 Compositional Knowledge  
5.1 Multitask Learning  
5.2 Lifelong Learning  
5.3 Nonmodular Compositional Works  
5.4 Understanding and Measuring Composition  
5.5 A Caveat on Compositional Learning Methods

6 Lifelong Reinforcement Learning

7 Compositional Reinforcement Learning

8 Summary and Directions for Future Work