«Material» relations have material structure on their own and include examples such as employments, kisses, enrollments, flight, connections and commitments. The relata of a material relation are mediated by individuals that are called relators. Relators («Relator») are individuals with the power of connecting entities; a flight connection, for example, founds a relator that connects airports, an enrollment is a relator that connects a student with an educational institution. Relators play an important role in answering questions of the sort: what does it mean to say that John is married to Mary? Why is it true to say that Bill works for Company X but not for Company Y?.

Material relations are derived (via «Derivation») from relators and the mediation relations that connect them to the corresponding relata. Cardinality constraints of mediation relations collapse by derivation. Material relations are always affected by collapsed cardinality). Also, several «Material» relations can be derived from a single «Relator» and «Mediation» relations.

Common questions

Ask us some question if something is not clear …



Example marriage


Example supervizor

For more examples see «Relator», «Derivation», «Mediation», and «Relator pattern».

Quoted from:

GUIZZARDI, Giancarlo. Ontological Foundations for Structural Conceptual Models. Enschede: CTIT, Telematica Instituut, 2005. GUIZZARDI, Giancarlo. Introduction to Ontological Engineering. [presentation] Prague: Prague University of Economics, 2011.