The Circumstantial Event Ontology (CEO) and ECB+/CEO: an Ontology and Corpus for Implicit Causal Relations between Events

The Circumstantial Event Ontology (CEO) and ECB+/CEO: an Ontology and Corpus for Implicit Causal Relations between Events Roxane Segers∗, Tommaso Caselli ∓, Piek Vossen ∗ ∗Vrije Universiteit Amsterdam, The Netherlands {r.h.segers, p.t.j.m.vossen}@vu.nl ∓Rijksuniversiteit Groningen, The Netherlands t.caselli@rug.nl Abstract In this paper, we describe the Circumstantial Event Ontology (CEO), a newly developed ontology for calamity events that models semantic circumstantial relations between event classes, where we define circumstantial as inferred implicit causal relations. The circumstantial relations are inferred from the assertions of the event classes that involve a change to the same property of a participant. Our model captures that the change yielded by one event, explains to people the happening of the next event when observed. We describe the meta model and the contents of the ontology, the creation of a manually annotated corpus for circumstantial relations based on ECB+ and the first results on the evaluation of the ontology. Keywords: Ontology, Event Modeling, Event Chaining, Causality, Annotated Corpora, Text Mining, Semantic Role Labeling 1. Introduction Suppose we read a sequence such as: ”Today was the burial of Mary Johnson, that was broadcasted live on TV. The pop star died last week when her yacht capsized and sunk af- ter hitting a tanker. Johnson was not wearing a life jacket and drowned.” As it is clear to most readers, but implicit in this sentence, there must be some relation between “hit”, “capsize”, “sinking”, “drown”, “die” and “burial”. The in- terpretation of this sentence as a text, i.e. a unitary mes- sage (De Beaugrande and Dressler, 1981), requires some coherence relations between the events, that are not explic- itly expressed. In the context of this occurrence, it is normal for a human reader to interpret the events as a chain of con- sequences. This coherence is the result of the fact that the events imply changes on a set of shared properties. We consider this type of relations between event pairs as a case of circumstantial relations, i.e. relations between events which allows interpreting their occurrence in the world, and in a text, as coherent. A circumstantial rela- tion makes clear “why” something happened, without nec- essarily predicting it. Circumstantial relations are a set of relations which include temporal, causal, entailment, pre- vention and contingency relations, among others. We distinguish two types of circumstantial relations: episodic and semantic. An episodic circumstantial rela- tion is a relation that holds between a pair of specific actual event instances in a specific context, where their connection is necessary to understand what is described in a meaning- ful and coherent way. For instance, the relation between the events “[a yacht] sunk” and “hitting [a tanker]” is a case of an episodic circumstantial relation: both events may hap- pen independently without implying the other necessarily, but when described in the same context, or circumstance, a connection is created that explains their occurrence as a dependent relation. On the other hand, we define semantic circumstantial re- lations as a relation that holds between event classes (ab- stracting …

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