Ontologies are formal knowledge representation methods that can provide means for a shared understanding of a given domain. To enable meaningful communication and interoperability between two or more information systems that utilize independently created ontologies, a bridge between them is necessary, often referred to as an ontology alignment. This book provides complete ontology alignment lifecycle, including modelling, methods, and maintenance processes. Summarizing the author's research from the past ten years, this book consolidates findings previously published in prestigious international journals and presented at leading conferences. Each book chapter is designed to be self-contained, allowing readers to approach the material modularly. The book introduces basic mathematical concepts, and later chapters build upon these foundations, but each focusses on specific aspects of ontology alignment, making the content accessible and easy to follow. Key Features: Includes formal definitions of ontologies and ontology alignment along with a set of methods for providing semantics of attributes and relations. Provides application of fuzzy logic in the task of ontology alignment. Contains methods of managing the evolution of ontologies and their alignments. Proposes novel methods of assessing the quality ontology alignment. Situated in the fields of knowledge representation and semantic technologies, this book is an invaluable resource for both academic researchers and practitioners, as well as students looking to deepen their understanding.