This paper presents the concept of a domain-oriented library of problem-solving methods, which consists of loosely coupled three modules for a domain ontology, problem-solving methods, and graphical user interfaces. A domain ontology provides fundamental concepts and their relations to be employed by the other two modules. Relations among concepts in a domain ontology help to articulate relationships between top-level problem-solving methods, which can not be clarified relying solely on data flow or control structure as in the conventional task-method decomposition hierarchies. A domain-oriented library of production scheduling methods, SCOOP, is then introduced, and its real-life application systems are briefly explained. Finally, empirical evaluation of the domain ontology in SCOOP is conducted, taking account of attributes and relations defined for domain concepts in the real applications.