On the role of thematic roles in a historical event ontology

In this paper we discuss the issues related to the formal representation of thematic roles in an ontology modeling historical events. We start by analyzing the ontological distinctions between thematic roles and social roles, which suggest different formal representations. Coupling the study of existing approaches with an analysis of historical texts - available within the Harlock'900 project - we propose a formal representation of thematic roles in HERO (Historical Event Representation Ontology), based on binary properties, directly connecting the event to its participants. Moreover, we show that a fine-grained formal ontological model of participation in (historical) events should include general thematic roles (e.g., agent, patient) -- able to capture the common aspects of the ways entities are involved in events -- and event-specific roles (e.g., sniper), introduced in the ontology according to a specific criterion, that guarantees the needed expressivity without proliferating roles. We conclude the paper by discussing the benefits of our approach.