The book presents logical foundations for rule-based systems, as seen by the Author. An attempt has been made to provide an in-depth discussion of logical and other aspects of such systems, including languages for knowledge representation, inference control, design and verification. The ultimate goal was to provide a deeper theoretical insight into the nature of rule-based systems and put together the most complete presentation including details so frequently skipped in typical textbooks. The book is divided into five main parts: 1) Logical Foundations of Rule-Based Systems; 2) Principles of Rule-Based Systems; 3) Verification of Rule-Based Systems; 4) Design of Rule-Based Systems; 5) Closing Remarks and Appendices.