# Core Ontology for Describing Production Equipment According to Intelligent Production
## 3 Materials and Methods  
To solve the problem, it is necessary to design a multi-level ontology, which will disclose the conceived concept. There is a certain set of hierarchy ontologies, which have their advantages and disadvantages. To achieve the objective, the authors chose a four-level ontology, shown in Figure 1. It is based on the classical three-level ontology of [PERSON] [29] with the addition of another core level. This choice provides a conceptually correct solution to the problem. The chosen four-level ontology contains: top-level ontology, core, domain ontology, application ontology (Figure 1). Each level of the hierarchy of ontology performs its functions, which ensures the development of high-quality conceptual models to represent the context of the subject  
Figure 1: Four-level hierarchy of ontology. area and its management. The overall objective of the paper is to systematize the theoretical knowledge and basic concepts of industrial enterprise in the form of core ontology, developed in accordance with the fundamental concept of BFO. The peculiarity of modern industrial ontologies is their focus on solving industrial problems. The article presents the results of the core ontology level development to determine the breakdowns typical for a unified piece of equipment, their locations, and the causes of occurrence in order to develop proactive actions. The developed industrial multilevel ontology contains a lot of heterogeneous static and dynamic information. Static information includes: description of industrial assets, methods of diagnosing the occurrence of equipment failures, expert information on the various characteristic types of failures and the main reasons for their occurrence. Dynamic information includes: equipment location and functions performed. The data collected from the equipment must be presented explicitly. The result of processing is information about their activities and state. The use of temporal relations between activities and spatial relations between assets and their location on the production in the ontology allows the simplification of algorithms for identifying the situation and the state of equipment. When designing the ontology, the authors focused on providing two main criteria: the possibility to reuse the modules of the conceptual model and the possibility to expand it. The top-level ontology is the fundamental basis for the construction of lower-level ontologies, because it provides definitions and terms common to all domains. That is, in fact, it provides a single consistent definition of terms for all subject areas [30]. Concretization and contextualization of each domain is done at the lower levels. BFO was chosen as the top-level ontology for several reasons:  
1. BFO is popular--hundreds of ontologies claim to use it as a top-level ontology;
2. It has a limited number of classes (terms), which is an advantage of top-level ontology. This indicates that it is understandable and easy to work with;
3. It includes definition of higher-level concepts only, which makes it universally applicable to any subject area;
4. It combines static and dynamic (temporal) parts in its composition;
5. It is in the process of standardization;
6. It is OWL-compatible. Figure 2 shows the implementation of a fragment of BFO (individual classes and their hierarchy), which is necessary to solve the task in Protege. At the second level, the core ontology was constructed. It represents a higher level of generic terms to cover and provide a definition for the broader domain. Its special feature is that it is related to the domain ontology and can be the result of several domain ontologies. Using a core ontology allows us to systematize the concept for domain ontology because it is a key prerequisite for it. Since the core combines a top-level and a domain-level ontology, its proper formation ensures that the latter is understandable and collision-free and prevents the redefinition of terms. In addition, it is possible to extend the ontology by adding derived or related domain ontologies.