This book introduces concepts, data structures, and algorithms for Preference Mining and Preference Repositories.Preferences and wishes occur everywhere in our daily life and therefore are crucial for the design of personalized applications. Preference Mining is a novel technology for the detection of preferences in the user's previous shopping or browsing behavior recorded in his log data. The Preference Repository defines an XML-structure for the persistent storage and access operations for the efficient management of user preferences.With these technologies as foundation personalized applications can improve their functionality by providing preference-based recommendations, personalized product notifications, and intelligent sales-explanation interfaces.