The lessons learned from experiments with early rule-based systems were not only that domain knowledge should be represented in an explicit way (such as the one supported by an ontology), but also that the problem-solving behaviour of a system should be carved out in a separate component of the system. The difficulty of finding the best alternative is often complex to resolve, especially it increases when it is necessary to consider alternative by several qualitatively different criteria. Available at the enterprises many information systems and decision support systems (DSS) are not able to fully meet the needs of managers because usually they represent a set of disparate databases, and the information in such systems is represented by text, or in the form of various directories and is characterized by a set of independent, uncoordinated and an implicitly expressed conceptual description of the system. Due to this it is necessary to have DSS that would provide decision makers information about the functions and mutual relations of the structural components of the company for their effective management. There are different approaches, models, and knowledge definition language for this but more and more popular recently become ontology engineering. The main idea of our approach is to separate the decision making method (method ontology) from the database (domain ontology) in the construction of ontology-based decision support system. Here, the problem of constructing domain ontology and method ontology appears. This paper focuses on constructing only method ontology.