This book constitutes revised selected papers from the workshops of the 4th Asia-Pacific Web and Web-Age Information Management International Joint Conference on Web and Big Data, APWeb-WAIM 2020: The Third International Workshop on Knowledge Graph Management and Applications, KGMA 2020; The Second International Workshop on Semi-structured Big Data Management and Applications, SemiBDMA 2020, and The First International Workshop on Deep Learning in Large-scale Unstructured Data Analytics, DeepLUDA 2020, held in Tianjin, China, in September 2020. Due to the COVID-19 pandemic the conference was held online.