Textbooks play a fundamental role in the learning process: to encourage the acquisition of new knowledge, they typically introduce the fundamental concepts before the advanced ones. Such an ordering of concepts is reflected in prerequisite relations, e. g. in dependency relations indicating which concepts a student must know before acquiring a new one. During the seminar the main challenges related to the recognition of prerequisite relationships starting from the content of didactic texts will be discussed. PREAP, a protocol for the construction of annotated resources enriched with prerequisite relationships, and a strategy for the automatic recognition of these relationships in didactic texts will be then introduced. The seminar will be concluded with an overview of the research issues still open and the illustration of PREAP potential in addressing such challenges.