Conference paper Open Access
Krieger, Hans Ulrich; Willms, Christian
n-ary relations (n ≥ 1) can in principle be realized through binary relations obtained by
a reiﬁcation process that introduces new individuals to which the additional arguments are linked
via accessor properties. Modern ontologies which employ standards such as RDF and OWL have
mostly obeyed this restriction, but have struggled with it nevertheless. Additional arguments for
representing, e.g., valid time, grading, uncertainty, negation, trust, sentiment, or additional verb roles
(for ditransitive verbs and adjuncts) are often better modeled in relation and information extraction
systems as direct arguments of the relation instance, instead of being hidden in deep structures.
In order to address non-binary relations directly, ontologies must be extended by Cartesian types,
ultimately leading to an extension of the standard entailment rules for RDFS and OWL. In order to
support ontology construction, ontology editors such as Prot´
ege´ have to be adapted as well.