To model reality by mapping its content to computable forms, we need to know how to represent the first-class entities of any existence, relationships, the adhesive of the world. Both human and machine understanding of the universe, its parts and realms, consists in knowing the cardinal relationships and underlying rules and making valid inferences from them. The Semantic Web ontology is often identified with a schema defining relationships between different resources. For instance, the OWL markup language is supposed to specify the types of relationships represented in RDF language employing an XML vocabulary, with a view to determine the relationships (and hierarchies) among diverse Web data resources identified by URI. And the formal specification of relationships determines the meaning (semantics) of knowledge domains, and the universality and credibility of any ontology, its rigor, cogency, validity, and richness, come from the capacity to fully describe all the possible types of relationships in a domain of knowledge or practice. Without a systematic theory of relations, it hardly is possible to form a universal account (language or theory) describing reality, its entity classes, properties, individuals with their particular properties, on which human or machine reasoning has to take place.