The Simple Event Model

Abstract

This document describes an ontology for events. The Simple Event Model (SEM) is created to model events in various subject domains.

The namespace for all terms in this ontology is: http://semanticweb.cs.vu.nl/2009/11/sem/

The RDF version of the ontology can be found at http://semanticweb.cs.vu.nl/2009/11/sem.rdf or by looking up http://semanticweb.cs.vu.nl/2009/11/sem/ with an HTTP accept header that includes application/rdf+xml.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document.

This document has been adapted from an academic paper [SEMDOC] published by the authors. It is a stable document and may be used as reference material or cited from another document.

Introduction

This document describes an ontology for modelling events. Events are central elements in the representation of data from a variety of domains. Examples of these domains are history, cultural heritage, geography and multimedia. Event-centered modeling captures the time and place aspects of a domain. In addition, events provide a way to describe complicated relations between people, places, actions and objects.

1. Overview of ontology
- 1.1 Example
2. Description and commentary
3. Namespaces
4. Ontology Reference
B. Acknowledgements
C. References
- C.1 Normative references
- C.2 Informative references

1. Overview of ontology

In this section we list the main elements of the SEM ontology. But first we give a simple example of how an event from the historical domain can be modeled in SEM.

1.1 Example

This example is based on a sentence, that represents a typical situation from the historical domain:

The Dutch launched the first police action in the Dutch East Indies in 1947; the Dutch presented themselves as liberators but were seen as occupiers by the Indonesian people.

This example is interesting because:

it contains conflicting views on the role of the actor: were the Dutch liberators or occupiers?
it makes explicit according to which authority the roles hold (the Dutch/Indonesian people)
it presents a challenge for modeling the type of the place involved: at that time the Dutch East Indies were an independent Republic according to the Indonesians, but according to the Dutch they were a ‘‘controlled region’’.

A pictorial illustration of the main classes and relationships in SEM is shown below. All terms are within the SEM namespace (http://semanticweb.cs.vu.nl/2009/11/sem/, preferred prefix sem:) unless an explicit prefix is given. The namespaces for all referenced vocabularies are giving in the section on Namespaces.

Diagram depicting core SEM classes and relationships

2. Description and commentary

SEM has been developed to on the one hand benefit from existing vocabularies and data sources that describe events, and on the other hand allowing a user to derive useful facts. Events, according to SEM, describe everything that happens, even fictional events. Becasue of its design SEM is capable of handling different viewpoints. In particular three aspects of viewpoints: (1) Event bounded roles, (2) time bounded validity of facts (e.g. time dependent type or role), and (3) attribution of the authoritative source of a statement.

3. Namespaces

The namespace for SEM is http://semanticweb.cs.vu.nl/2009/11/sem/. SEM extends and uses terms from other vocabularies. A full set of alphabetically ordered namespaces and prefixes used in this document is shown in the table below.

Prefix	Namespace	Reference
rdf	http://www.w3.org/1999/02/22-rdf-syntax-ns#	[RDF-CONCEPTS]
rdfs	http://www.w3.org/2000/01/rdf-schema#	[RDF-SCHEMA]
skos	http://www.w3.org/2004/02/skos/core#	[SKOS-REFERENCE]
foaf	http://xmlns.com/foaf/0.1/	[FOAF]
dcterms	http://purl.org/dc/terms/	[DC11]
dctype	http://purl.org/dc/dcmitype/	[DCTYPE]
dolce	http://www.loa-cnr.it/ontologies/DOLCE-Lite.owl#	[DOLCE]
cidoc	http://www.cidoc-crm.org/rdfs/cidoc_crm_v5.0.4_english_label.rdfs	[CIDOC]
cyc	http://sw.opencyc.org/2009/04/07/concept/en/	[CYC]
sumo	http://www.ontologyportal.org/translations/SUMO.owl.txt#	[SUMO]
eo	http://purl.org/NET/c4dm/event.owl#	[EO]
WGS84	http://www.w3.org/2003/01/geo/wgs84_pos#	[WGS84]
time	http://www.w3.org/2006/time	[TIME]

4. Ontology Reference

SEM’s classes are divided in three groups: core classes, types, and constraints. The four core classes are: sem:Event (to record what happens), sem:Actor (who or what participated in the event), sem:Place (where did it happen), sem:Time (when did it happen). Every core class has an associated sem:Type class that contains resources that describe the type of a core individual.

SEM’s properties are divided in three kinds: sem:eventProperty, sem:type properties and a few other properties like sem:accordingTo and sem:hasTimeStamp’s subproperties.
The sem:eventProperty relates sem:Events to other individuals.
A sem:type relates individuals of the sem:Core class to individuals of sem:Type. There are subproperties of sem:type for each of the separate core classes to facilitate querying.
To represent opinions sem:accordingTo relates a sem:View to a sem:Authority.

Time is an important part of SEM. There are seven properties that represent time stamps. One for single time values, sem:hasTimeStamp; two for time intervals, sem:hasBeginTimeStamp and sem:hasEndTimeStamp; and four for uncertain time intervals, sem:hasEarliestBeginTimeStamp, sem:hasLatestBeginTimeStamp, sem:hasEarliestEndTimeStamp, and sem:hasLatestEndTimeStamp. The latter kind of intervals is meant to describe any kind of uncertainty about the begin or end of a period. It does not imply a fuzzy interpretation of time. Open-ended intervals can be expressed by omitting begin or end timestamps.

4.1 Index of classes and properties

4.1 SEM Core

The four core classes Event, Actor, Place and time record the main variables of an Event: what happens, who or what participated, where did it happen and when.

4.1.1 Class: Core

The Core class contains all entities that make up the context of an event.

OWL Class:	sem:Core
subClassOf:	owl:Thing
Usage note:	The SEM Core class contains all entities that make up the context of an event: Events, Actors, Places, Times. This class is meant to be extended for each application domain.

4.1.2 Class: Actor

The Actor class holds individuals that take part in an event.

OWL Class:	sem:Actor
subClassOf:	sem:Core sem:Authority
skos:broadMatch:	cyc:SomethingExisting dolce:endurant
skos:closeMatch:	cidoc:E39.Actor cyc:Agent-Generic dcterms:Agent dcterms:AgentClass foaf:Agent sumo:Agent
Usage note:	Actors are entities that take part in an Event, either actively or passively. Actors do not necessarily have to be sentient. They can also be objects. Actors are a thing, animate or inanimate, physical or non-physical.

4.1.3 Class: Object

Objects are passive, inanimate Actors.

OWL Class:	sem:Object
subClassOf:	sem:Actor
skos:broadMatch:	cyc:SomethingExisting dolce:endurant
skos:closeMatch:	cidoc:E19.Physical_Object E21.Person sumo:Object
skos:narrowMatch:	dcterms:PhysicalResource dcterms:PhysicalObject eo:Factor eo:Product
Usage note:	Objects are passive, inanimate Actors.

Property: actorType

Actor type is used to assign a type to an actor.

OWL Property:	sem:actorType
Domain:	sem:Actor
Range:	sem:ActorType

Property: hasActor

Has actor is used to state which Actors or Objects participate in an Event.

OWL Property:	sem:hasActor
Range:	sem:Actor
subPropertyOf:	sem:type

4.1.4 Class: Event

Events are things that happen. This comprises everything from historical events to web site sessions and mythical journeys. Event is the central class of SEM.

OWL Class:	sem:Event
subClassOf:	sem:Core
skos:broadMatch:	eo:Event lode:Event
skos:closeMatch:	cidoc:E5.Event cyc:Situation dctype:Event dolce:perdurant sumo:Process
Usage note:	Events are things that happen. This comprises everything from historical events to web site sessions and mythical journeys. Event is the central class of SEM.

Property: eventProperty

Event properties connect Events to other SEM Core entities.

OWL Property:	sem:eventProperty
Domain:	none
Range:	none

Property: eventType

Has event type is used to assign a type to an event.

OWL Property:	sem:eventType
Domain:	sem:Event
Range:	sem:EventType
subPropertyOf:	sem:type

Property: hasSubEvent

Has subevent connects an Event to other Events that belong to it. This is a very generic property that does not mean the subevents fully define the superconcept or that there is any causal relationship.

OWL Property:	sem:hasSubEvent
Domain:	sem:Event
Range:	sem:Event
subPropertyOf:	sem:eventProperty
inverseOf:	sem:subEventOf

Property: subEventOf

Inverse property of hasSubEvent

OWL Property:	sem:subEventOf
Domain:	sem:Event
Range:	sem:Event
subPropertyOf:	sem:eventProperty
inverseOf:	sem:hasSubEvent

4.1.5 Class: Place

Places are locations where an Event happens. They do not need to be physical places and hence do not necessarily need coordinates. Neither do they need to have any significance apart from them being the location of an Event.

OWL Class:	sem:Place
subClassOf:	sem:Core
skos:closeMatch:	cidoc:E53.Place cyc:EnduringThing-Localized dcterms:Location sumo:GeographicArea
skos:narrowMatch:	dolce:PhysicalRegion wgs84:SpatialThing
Usage note:	Places are locations where an Event happens. They do not need to be physical places and hence do not necessarily need coordinates. Neither do they need to have any significance apart from them being the location of an Event.

Property: hasPlace

hasSubType is used to state that a type falls under another type. This is a generic aggregation relation that is used to generalize over various hierarchical relations that can exist between types.

OWL Property:	sem:hasPlace
Range:	sem:Place
subPropertyOf:	sem:eventProperty

Property: placeType

Has place type is used to assign a type to a place.

OWL Property:	sem:placeType
Domain:	sem:Place
Range:	sem:PlaceType
subPropertyOf:	sem:type

4.1.6 Class: Time

Time contains symbolic representations of when an Event took place. Time instances do not necessarily need to have a timestamp associated with them. The Time class exists to represent semantics of time, e.g. that one thing happens before another, even though the exact timestamps are unknown.

OWL Class:	sem:Time
subClassOf:	sem:Core
skos:broadMatch:	time:TemporalEntity
Usage note:	Time contains symbolic representations of when an Event took place. Time instances do not necessarily need to have a timestamp associated with them. The Time class exists to represent semantics of time, e.g. that one thing happens before another, even though the exact timestamps are unknown.

Property: hasTime

Has time is used to indicate at which time an Event took place or when a property under the Temporary Constraint is valid. Has time points to a symbolic representation of time, which allows semantic relations between time resources. (see http://www.w3.org/TR/owl-time/)

OWL Property:	sem:hasTime
Range:	sem:Time
subPropertyOf:	sem:eventProperty

Property: timeType

Has time type is used to assign a type to a time individual.

OWL Property:	sem:timeType
Domain:	sem:Time
Range:	sem:TimeType
subPropertyOf:	sem:type

Property: hasTimeStamp

Has timestamp is used to put time indicators on any individual. It is the most common way to state when an Event took place. There are subproperties of hasTimeStamp to represent time intervals and uncertain time intervals. If the exact moment is not known, but it is necessary to specify a certain time, use hasTime instead. All of these properties are also used to indicate the time at which a property under the Temporary Constraint is valid.

OWL Property:	sem:hasTimeStamp
Domain:	none
Range:	none

Property: hasBeginTimeStamp

Has begin timestamp is used to indicate the beginning of a time interval. Omitting the hasBeginTimeStamp while stating a hasEndTimeStamp is interpreted as an open ended interval.

OWL Property:	sem:hasBeginTimeStamp
subPropertyOf:	sem:hasTimeStamp

Property: hasEarliestBeginTimeStamp

Has earliest begin timestamp is used to indicate the earliest possible starting time of an uncertain time interval.

OWL Property:	sem:hasEarliestBeginTimeStamp
subPropertyOf:	sem:hasBeginTimeStamp

Property: hasLatestBeginTimeStamp

Has latest begin timestamp is used to indicate the latest possible starting time of an uncertain time interval.

OWL Property:	sem:hasLatestBeginTimeStamp
subPropertyOf:	sem:hasBeginTimeStamp

Property: hasEndTimeStamp

Has end timestamp is used to indicate the end of a time interval. Omitting the hasEndTimeStamp while stating a hasBeginTimeStamp is interpreted as an open ended interval.

OWL Property:	sem:hasEndTimeStamp
subPropertyOf:	sem:hasTimeStamp

Property: hasEarliestEndTimeStamp

Has earliest end timestamp is used to indicate the earliest possible ending time of an uncertain time interval.

OWL Property:	sem:hasEarliestEndTimeStamp
subPropertyOf:	sem:hasEndTimeStamp

Property: hasLatestEndTimeStamp

Has latest end timestamp is used to indicate the latest possible ending time of an uncertain time interval.

OWL Property:	sem:hasLatestEndTimeStamp
subPropertyOf:	sem:hasEndTimeStamp

4.2 Authorities

Authorities are used to specify according to whom a statement is valid. Individuals of the class sem:Authority can be sem:Actors but do not necessarily have to be. They can also symbolize data sources. The sem:Authority class is meant as a means for provenance and trust reasoning.

4.2.1 Class: Authority

Authorities are entities that state SEM properties. Their nature is not specified, they can symbolize people, organizations, sources of information, etc.

OWL Class:	sem:Authority
subClassOf:	owl:Thing
Usage note:	Authorities are entities that state SEM properties. Their nature is not specified. They can symbolize people, organizations, sources of information, etc.

Property: accordingTo

According to is used to state which Authority says that a property constrained by the View Constraint is true.

OWL Property:	sem:accordingTo
Domain:	sem:View
Range:	sem:Authority

4.3 Constraints

There are three kinds of Constraints: Role, Temporary and View. sem:Role describes the role that an individual of a class is playing in the context of a specific event. Roles can be specified for all Core individuals. In the example of the Dutch East Indies roles can be specified for Actors (e.g. ‘‘occupier’’) as well as Places (‘‘capital city’’, dbpedia:Colony).

Temporary defines the temporal boundary within which a property holds, for example, the type of the Place ‘‘Indonesia’’ as a ‘‘republic’’ holds from 1945 on, at least according to the Indonesians. This notion can be modeled with sem:View. sem:View is used to record points of view and opinions. Indonesia, in 1947, has either the type ‘‘republic’’ or ‘‘controlled region’’, depending on the source of information. This is modeled as a sem:View constraint on the property (sem:placeType in this case) that holds sem:accordingTo a sem:Authority (respectively the Indonesian People or the Netherlands).

4.3.1 Class: Constraint

The SEM Constraint class contains instances of properties that have a constrained validity. This includes time dependent validity (sem:Temporary), validity in the guise of a specific role (sem:Role), or validity according to a given Authority (sem:View).

OWL Class:	sem:Constraint
subClassOf:	owl:Thing
Usage note:	The SEM Constraint class contains instances of properties that have a constrained (i.e. not universal) validity. This includes time dependent validity (Temporary), validity in the guise of a specific role (Role), or validity according to a given Authority (View).

4.3.2 Class: Role

Roles are properties with a subspecified function or position indicated by a RoleType in the scope of an Event. For example, the sem:hasActor property can be subspecified with the RoleType attacker, to denote that the type of participation of the Actor in the scope of the Event is "attacker". The sem:hasPlace property can be subspecified with the RoleType origin, to denote that within the scope of the Event it is the origin.

OWL Class:	sem:Role
subClassOf:	sem:Constraint
skos:relatedMatch:	cyc:Role dolce:region sumo:IntentionalProcess
Usage note:	Roles are properties with a subspecified function or position indicated by a RoleType in the scope of an Event.

Property: roleType

Has role type is used to assign a role type to a Role property constraint. This role is a subspecification of the eventProperty which it constrains. For example, if an Event hasActor an Actor and this property is given a Role Constraint, then roleType can be used to assign a role to the participation of the Actor in the Event indicated by hasActor.

OWL Property:	sem:roleType
Domain:	sem:Role
Range:	sem:RoleType
subPropertyOf:	sem:type

4.3.3 Class: Temporary

Temporaries are properties that only hold during a certain Time, which is either indicated with the sem:hasTime property to an instance of sem:Time, or with the sem:hasTimeStamp property to some timestamp(s).

OWL Class:	sem:Temporary
subClassOf:	sem:Constraint
Usage note:	Temporaries are properties that only hold during a certain Time, which is either indicated with the sem:hasTime property to an instance of sem:Time, or with the sem:hasTimeStamp property to some timestamp(s).

4.3.4 Class: View

Views are properties that only hold according to a certain Authority.

OWL Class:	sem:View
subClassOf:	sem:Constraint
Usage note:	Views are properties that only hold according to a certain Authority.

4.4 Types

For any given application SEM contains a typing system in order to query events at a relevant level of abstraction. To be able to reuse any vocabulary on the Web to pick our types from, regardless of how the concepts in these vocabularies are modeled SEM allows types to be both individuals or classes. This way we can borrow type identifiers from any vocabulary.

4.4.1 Class: Type

The SEM Type class contains all types of Core instances. These can be either individuals of classes themselves. This class is meant to be extended for each application domain.

OWL Class:	sem:Type
subClassOf:	owl:Thing
skos:closeMatch:	cidoc:E55.Type dolce:AbstractRegion
Usage note:	The SEM Type class contains all types of Core instances. These can be either individuals of classes themselves. This class is meant to be extended for each application domain.

Property: hasSubType

Has sub type is used to state that a type falls under another type. This is a generic aggregation relation that is used to generalize over various hierarchical relations that can exist between types.

OWL Property:	sem:hasSubType
Domain:	sem:Type
Range:	sem:Type
inverseOf:	sem:subTypeOf

Property: subTypeOf

The inverse property of hasSubType.

OWL Property:	sem:subTypeOf
inverseOf:	sem:hasSubType

Property: type

Type is the super property of the properties that are used to indicate the type of a Core instance, eventType, actorType, placeType, timeType; and of roleType. Types can be both classes and individuals, cf. OWL 2 punning.

OWL Property:	sem:type
Range:	sem:Type
subPropertyOf:	rdf:type

4.4.2 Class: ActorType

ActorType contains all resources that are used to classify Actors, e.g. person

OWL Class:	sem:ActorType
subClassOf:	sem:Type
Usage note:	ActorType contains all resources that are used to classify Actors, e.g. person

4.4.3 Class: EventType

EventType contains all resources that are used to classify Events, e.g. meeting

OWL Class:	sem:EventType
subClassOf:	sem:Type
Usage note:	EventType contains all resources that are used to classify Events, e.g. meeting

4.4.4 Class: PlaceType

PlaceType contains all resources that are used to classify Places, e.g. river.

OWL Class:	sem:PlaceType
subClassOf:	sem:Type
Usage note:	PlaceType contains all resources that are used to classify Places, e.g. river.

4.4.5 Class: RoleType

RoleType contains all resources that are used to classify Roles, e.g. receiver.

OWL Class:	sem:RoleType
subClassOf:	sem:Type
Usage note:	RoleType contains all resources that are used to classify Roles, e.g. receiver.

4.4.6 Class: TimeType

TimeType contains all resources that are used to classify Time, e.g. century.

OWL Class:	sem:TimeType
subClassOf:	sem:Type
Usage note:	TimeType contains all resources that are used to classify Time, e.g. century.

B. Acknowledgements

Part of this work has been carried out as a part of the Poseidon project in cooperation with Thales Nederland under the responsibilities of the Embedded Systems Institute (ESI). This project is partially supported by the Dutch Ministry of Economic Affairs under the BSIK03021 program.

C. References

C.1 Normative references

[RDF-SCHEMA]: Dan Brickley; Ramanathan Guha. RDF Schema 1.1. 9 January 2014. W3C Proposed Edited Recommendation. URL: http://www.w3.org/TR/rdf-schema/
[RDF-SPARQL-QUERY]: Eric Prud'hommeaux; Andy Seaborne. SPARQL Query Language for RDF. 15 January 2008. W3C Recommendation. URL: http://www.w3.org/TR/rdf-sparql-query/
[SKOS-REFERENCE]: Alistair Miles; Sean Bechhofer. SKOS Simple Knowledge Organization System Reference. 18 August 2009. W3C Recommendation. URL: http://www.w3.org/TR/skos-reference
[FOAF]: Dan Brickley, Libby Miller. FOAF Vocabulary Specification 0.98. 9 August 2010. URL: http://xmlns.com/foaf/spec/
[OWL2-PRIMER]: Pascal Hitzler; Markus Krötzsch; Bijan Parsia; Peter Patel-Schneider; Sebastian Rudolph. OWL 2 Web Ontology Language Primer (Second Edition). 11 December 2012. W3C Recommendation. URL: http://www.w3.org/TR/owl2-primer/
[RDF-CONCEPTS]: Graham Klyne; Jeremy Carroll. Resource Description Framework (RDF): Concepts and Abstract Syntax. 10 February 2004. W3C Recommendation. URL: http://www.w3.org/TR/rdf-concepts/
[DC11]: Dublin Core metadata initiative. Dublin Core metadata element set, version 1.1. July 1999. Dublin Core recommendation. URL: http://dublincore.org/documents/dcmi-terms/
[DCTYPE]: DCMI Metadata Terms. DCMI Type Vocabulary . URL: http://dublincore.org/documents/2012/06/14/dcmi-terms/?v=dcmitype
[CYC]: OpenCyc for the Semantic Web. URL: http://sw.opencyc.org/
[DOLCE]: DOLCE : a Descriptive Ontology for Linguistic and Cognitive Engineering. URL: http://www.loa.istc.cnr.it/old/DOLCE.html
[CIDOC]: The CIDOC Conceptual Reference Model (CRM) provides definitions and a formal structure for describing the implicit and explicit concepts and relationships used in cultural heritage documentation. URL: http://www.cidoc-crm.org/index.html
[SUMO]: The Suggested Upper Merged Ontology (SUMO). URL: http://www.ontologyportal.org/
[EO]: The Event Ontology, developed in the Centre for Digital Music in Queen Mary, University of London URL: http://motools.sourceforge.net/event/event.html
[WGS84]: W3C Basic Geo (WGS84 lat/long) Vocabulary. URL: http://www.w3.org/2003/01/geo/
[TIME]: W3C Time Ontology. URL: http://www.w3.org/TR/owl-time/

C.2 Informative references

[turtle]: Eric Prud'hommeaux; Gavin Carothers. RDF 1.1 Turtle. 9 January 2014. W3C Proposed Recommendation. URL: http://www.w3.org/TR/turtle/
[SEMDOC]: Willem Robert van Hage, Véronique Malaisé, Roxane Segers, Laura Hollink, Guus Schreiber. Design and use of the Simple Event Model (SEM). Web Semantics: Science, Services and Agents on the World Wide Web 9 (2011) 128–136 URL: http:/ /www.elsevier.com/ locate/websem

The Simple Event Model Ontology