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“An ontology is a formal, explicit specification of a shared conceptualization” (Studer et al., 1998).

  • Formal: machine readable
  • Explicit: the type of concepts used, and the constraints on their use, are explicitly defined
  • Shared: captures knowledge in a way that is accepted by a group
  • Conceptualization: an abstract model of some phenomenon in the world by having identified the relevant concepts of that phenomenon

Philosophically, ontology is the study of being: of what pieces fit together to make up the world and how those parts interrelate. In the domain of computer and information sciences, and in relation to Linked Data (LD), it is the formalization of this concept in a machine-readable way: a model of a domain—the parts that make it up and how they fit together—written in a way that can be understood by computers. An ontology formally captures and structures knowledge of the entities, properties, and relationships that make up a domain so that this conceptualization can be shared and reused by others. Ontologies are an important element to many computing fields, including object-oriented software system design, information retrieval systems, and a number of tasks in the field of artificial intelligence. Ontologies are also a key part of the Semantic Web, as they are used to formally define the meanings of used terminology and the relationship of those terms to other concepts and vocabularies.

DescribesConcepts (content) and the relationships between them (structure), including axioms and restrictionsHierarchical relationships among concepts, and specifies the term to be used to refer to eachHierarchical and non-hierarchical relationships among conceptsGeneral term for a collection of concepts (words) to do with a domain
RelationshipsTyped hierarchical and associativeBasically hierarchical, but all modeled using same notationUntyped hierarchical, associative, and equivalenceUnspecified (abstract concept)
PropertiesRDFS defines relationship properties and restrictionsNoneCan be described in scope notes if requiredUnspecified (abstract concept)
StructuredNetworkTreeCross-branch treeUnspecified (abstract concept)


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