Knowledge is the most important aspect of the human mind and it is also the heart of any intelligent systems. Like humans, knowledge enables systems to make decisions, take actions, evaluate situations, and infer new knowledge not explicitly represented. This book introduces how to represent knowledge through ontologies which is one of the most popular knowledge representation languages for intelligent systems. The book also proposes a solution for one of the most important ontology change issues called ontology evolution. The solution allows intelligent systems´ knowledge to evolve automatically without intervention of ontology engineers. Moreover, it addresses the negative consequences of automatic evolution by providing new methods to avoid their occurrences and keeping the knowledge in a coherent and consistent state. However, the book gives a good background to readers and researchers who want to have a wide view on basics of knowledge, ontologies, different methods of ontology interoperability, and the consistency issues of ontologies. In addition, this book is presented to readers and researchers who have interests in exploiting knowledge with smart systems.