Multi-Label Lifelong Machine Learning: A Scoping Review of Algorithms, Techniques, and Applications

Lifelong machine learning concerns the development of systems that continuously learn from diverse tasks, incorporating new knowledge without forgetting the knowledge they have previously acquired. Multi-label classification is a supervised learning process in which each instance is assigned multiple non-exclusive labels, with each label denoted as a binary value. One of the main challenges within the lifelong learning paradigm is the stability-plasticity dilemma, which entails balancing a model's adaptability in terms of incorporating new knowledge with its stability in terms of retaining previously acquired knowledge. When faced with multi-label data, the lifelong learning challenge becomes even more pronounced, as it becomes essential to preserve relations between multiple labels across sequential tasks. This scoping review explores the intersection of lifelong learning and multi-label classification, an emerging domain that integrates continual adaptation with intricate multi-label datasets. By analyzing the existing literature, we establish connections, identify gaps in the existing research, and propose new directions for research to improve the efficacy of multi-label lifelong learning algorithms. Our review unearths a growing number of algorithms and underscores the need for specialized evaluation metrics and methodologies for the accurate assessment of their performance. We also highlight the need for strategies that incorporate real-world data from varying contexts into the learning process to fully capture the nuances of real-world environments.