This book presents the first integrated approach to design, implement and test a computer-based system for assessing textual complexity, learning strategies as well as learner collaborative contributions. The proposed approach, based on the most advanced natural language processing techniques, aims to provide a qualitative estimation of the learning process that considers both the individual and the collaborative aspects of learning. The work is highly interdisciplinary and integrates computer science, cognitive science, linguistics (mainly NLP) and educational research. The book includes both new theories and their experimental validation.