Information access systems, such as search engines, recommender systems, and conversational assistants, have become integral to our daily lives as they help us satisfy our information needs. However, evaluating the effectiveness of these systems presents a complex scientific challenge, rooted in the difficulty of assessing a system's overall effectiveness in assisting users to complete tasks through interactive support, and by the substantial variation in user behaviour and preferences.

This monograph focuses on providing a thorough understanding of user simulation techniques designed specifically for evaluation purposes. The authors begin with a background of information access system evaluation and explore the diverse applications of user simulation.

Subsequently, they systematically review the major research progress in user simulation, covering both general frameworks for designing user simulators, utilizing user simulation for evaluation, and specific models and algorithms for simulating user interactions with search engines, recommender systems, and conversational assistants. Realizing that user simulation is an interdisciplinary research topic, whenever possible, the authors establish connections with related fields, including machine learning, dialogue systems, user modelling, and economics.

This monograph provides a systematic review of user simulation techniques aimed at giving designers methods for successfully evaluating and improving modern information access systems. .