A model is a consistent set of formal elements that describe an entity. The model helps in solving a number of problems, for example, creating interfaces between a system and a person, and a rough estimate of the system's efficiency.
A domain model (DM) is a part of the real world, displayed as a class or set of classes of real objects.
The construction of the subject area (SbA) model is based on the concept of ontology (the science of being, the science of the nature of things and the relationship between them). From the standpoint of artificial intelligence, the term ontology can be used to define a certain mechanism, a method that is used to describe the SbA, in particular, the basic concepts of this area, their properties and relationships between them. In other words, the ontology consists of the SbD objects divided into clusters according to certain criteria, their definitions and attributes, as well as the inference rules associated with them. The ontology is encoded in such a way that objects and properties are available to software agents.
There is no clear boundary between the knowledge base and the ontology of the SbA. Ontologies can be used to represent knowledge about SbA concepts and hypothesized relationships between them, as well as to describe the content of Web pages. In addition, ontologies can be used to build knowledge bases not only for expert systems, but also for any other applications.
