The paper introduces Frame Logic (F-logic), a formalism designed to capture the structural aspects of object-oriented and frame-based languages in a clean and declarative manner. F-logic addresses key features such as object identity, complex objects, inheritance, polymorphic types, query methods, encapsulation, and others. It stands in the same relationship to the object-oriented paradigm as classical predicate calculus stands to relational programming. F-logic has a model-theoretic semantics and a sound and complete proof theory. The paper discusses the relationship between object-oriented and relational paradigms, the syntax and semantics of F-logic, and its applications in database schema definition, querying, and manipulation. It also explores extensions of F-logic, including its combination with other logics like HiLog and Transaction Logic, and its use in modeling complex values, version control, and path expressions. The paper concludes by providing a retrospective view of F-logic's internal structure and its connection to classical predicate calculus.The paper introduces Frame Logic (F-logic), a formalism designed to capture the structural aspects of object-oriented and frame-based languages in a clean and declarative manner. F-logic addresses key features such as object identity, complex objects, inheritance, polymorphic types, query methods, encapsulation, and others. It stands in the same relationship to the object-oriented paradigm as classical predicate calculus stands to relational programming. F-logic has a model-theoretic semantics and a sound and complete proof theory. The paper discusses the relationship between object-oriented and relational paradigms, the syntax and semantics of F-logic, and its applications in database schema definition, querying, and manipulation. It also explores extensions of F-logic, including its combination with other logics like HiLog and Transaction Logic, and its use in modeling complex values, version control, and path expressions. The paper concludes by providing a retrospective view of F-logic's internal structure and its connection to classical predicate calculus.