Learning Attributes and Relations

Besides being described by their position in a taxonomy, concepts are also characterized by attributes as well as by relations to other concepts. In the context of this book, we will restrict ourselves to binary relations establishing a connection between different concepts at the schema level. In order to provide useful inferences, these relations need to be further axiomatically defined and combined with other relations or concepts in the form of rules. The learning of corresponding axioms or rules is, however, out of the scope of this book. We will focus on learning relations at the schema level. In what follows, we first present the most common approaches to learning relations from text in order to situate our work in the context of the state-of-the-art in the field.