The components of ontology are individuals, classes, attributes and relationships. In ontology, concepts refer to objects, which will be organized, attributes are the traits of the objects, relationships connect two concepts and instances are the actual data in an information system .
Components of ontology:  The components of ontology are
Individuals are also referred to as instances. They are the basic “ground level” components of ontology. The individuals in an ontology may include concrete objects such as people, animals, tables, automobiles, molecules, and planets, as well as abstract individuals such as numbers and words.
Classes are also referred to as concepts. Concepts are type, sort, category which include the abstract groups, sets and collection of objects. Ontologies vary based on whether a class can contain other class or whether a class can belong to itself.
A class can be subsumed to another classes which is called as a subclass. The subsumption relation creates hierarchy of classes. The parent class is the subsuming class and the subclass is the subsumed class. The subsumed class (subclass) inherits the properties from the subsuming class (parent class). This means, anything that is necessarily true about the parent class must be necessarily true in a subsumed child class. In ontologies, the class which has a single parent is considered as single inheritance where as if a class has many parents it is considered as multiple inheritances. In multiple inheritances all necessary properties of the subsuming classes are inherited by subsumed class.
Attributes are used to describe an object. The attributes have a name and a value.and is used to store information that is specific to the object.
Relation connects two concepts or an object to a property. The most important relation in ontology is the subsumption relation which includes “is-super class-of, is-subclass-of” and others. This defines which objects are members of class of objects. The is-a relationship creates hierarchical taxonomy, a tree like structure that clearly shows how objects are related to each other. Another type of relation is “part-of”, which represents how objects are combined to form composite objects.
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