The Lifelog Search Challenge (LSC) is an interactive benchmarking evaluation workshop for lifelog retrieval systems. The challenge was first organised in 2018 aiming to find the system that can quickly retrieve relevant lifelog images for a given semantic query. This paper provides an analysis of the performance of all 17 systems participating in the 4th LSC workshop held at the 2021 Annual ACM International Conference on Multimedia Retrieval (ICMR). LSC'21 was the largest effort at comparing different approaches to interactive lifelog retrieval systems seen thus far. Findings from the challenge suggest that many different interactive factors contribute to the success (or otherwise) of participating teams. In this paper, we provide an overview of the LSC'21 challenge, introduce each team's approach and explore these factors in depth and offer clues on how to develop a high-performing interactive lifelog search engine.
INDEX TERMS lifelog, information retrieval, multimodal, analyticsAt LSC'21, each of the participating teams brought a unique and customised search engine to the challenge. In this paper, we introduce the LSC challenge, describe all competing systems, and highlight the techniques and components that are employed in state-of-the-art interactive lifelog