From the Greek words "onto" and "logia," which means the study of being (that which is), an ontology defines the relationships between things. The terms taxonomy and ontology are often used to represent a formal classification of some subject; however, a taxonomy typically defines one category of items in a hierarchical tree structure; whereas an ontology shows the relationships between items in different categories in a graph model.
There are numerous vocabularies on the Web that define the data interrelationships on the Semantic Web. Whereas the World Wide Web links Web pages together, the Semantic Web links the data on the Web that are related. See taxonomy
, linked open data
and Semantic Web