Extensions to the OWL-Time Ontology

OWL-Time [[owl-time]] is an ontology for temporal entities and relations between them. OWL-Time defines simple temporal entities (intervals and instants). This note adds one new class time:TemporalAggregate and two properties time:hasPart and its inverse time:isPartOf to allow for the description of arbitrary aggregates of temporal entities.

The namespace for OWL-Time terms is http://www.w3.org/2006/time#

The suggested prefix for the OWL-Time namespace is time

The OWL-Time ontology is available here.

The OWL-Time ontology with these extensions is available here.

For OGC - This is a Public Draft of a document prepared by the Spatial Data on the Web Interest Group (SDWIG) — a joint W3C-OGC project (see charter). The document is prepared following W3C conventions. This document is not an OGC Standard. This document is distributed for review and comment. This document is subject to change without notice and may not be referred to as an OGC Standard. Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation.

New classes and properties are introduced in this extension to OWL-Time. The new elements concern temporal entities which cannot be expressed in OWL-Time. The ontology document imports OWL-Time, and adds the new elements and axioms. IRIs denoting the new elements are placed in the OWL-Time namespace since it is expected that they could be added to the normative ontology in a future revision of OWL-Time.

Motivation and background

OWL-Time is an ontology for describing temporal entities and their relationships [[owl-time]]. The focus is particularly in relationships between time intervals, using the terminology originally defined by Allen [[?al-84]] [[?af-97]]. OWL-Time includes direct implementation of the following classes that were identified by Allen:

General temporal entities: time:TemporalEntity
General intervals: time:Interval
Proper intervals, whose beginning and end are distinct: time:ProperInterval
Instants, which are entities whose beginning and end cannot be distinguished: time:Instant

A summary of the semantics of the temporal entities is provided in OWL-Time Figure 1.

However, many applications involve multiple time instants and intervals, which it is convenient to identify as a single entity, but which is assembled from from multiple member entities. This note defines an additional temporal entity, the time:TemporalAggregate which is composed of an explicit set of individual time:TemporalEntitys. A summary of the model is shown in .

temporal aggregate — The new class :TemporalAggregate is composed of one or more :TemporalEntity parts

Future extensions may define additional aggregate and composite structures, for example as regular, recurring sequences.

Notation and namespaces

Classes and properties are denoted in this specification using Compact URIs [[?curie]].

The namespace for all classes and properties in OWL-Time and this extension is http://www.w3.org/2006/time#.

The table below indicates the full list of namespaces and prefixes used in this document.

Prefix	Namespace
`dcterms`	`http://purl.org/dc/terms/`
`ex`	`http://example.org/time/`
`owl`	`http://www.w3.org/2002/07/owl#`
`rdf`	`http://www.w3.org/1999/02/22-rdf-syntax-ns#`
`rdfs`	`http://www.w3.org/2000/01/rdf-schema#`
`time`	`http://www.w3.org/2006/time#`

Where class descriptions include local restrictions on properties, these are described using the OWL 2 Manchester Syntax [[owl2-manchester-syntax]].

Examples and other code fragments are serialized using RDF 1.1 Turtle notation [[turtle]].

Vocabulary specification

Classes

Temporal aggregate

Class:	`time:TemporalAggregate`
IRI:	`http://www.w3.org/2006/time#TemporalAggregate`
Definition:	A temporal aggregate is temporal entity that is an aggregation of one or more temporal entities
Instance of:	`owl:Class`
Sub-class of:	`time:TemporalEntity`
Restrictions:	`time:hasPart min 1`

Properties

has a part

Property:	`time:hasPart`
IRI:	`http://www.w3.org/2006/time#hasPart`
Definition:	Link to a temporal entity that is a part of this temporal aggregate
Instance of:	`owl:ObjectProperty`
Sub-property of:	`rdfs:member`
Sub-property of:	`dcterms:hasPart`
Domain:	`time:TemporalAggregate`
Range:	`time:TemporalEntity`

is a part of

Property:	`time:isPartOf`
IRI:	`http://www.w3.org/2006/time#isPartOf`
Definition:	Link to a temporal aggregate of which this temporal entity is a part
Instance of:	`owl:ObjectProperty`
Inverse of:	`time:hasPart`
Domain:	`time:TemporalEntity`
Range:	`time:TemporalAggregate`

Examples

Example instances showing the use of the TemporalAggregate class are available in this repository.

School terms

In the Australian state of Victoria, the public school year is composed of four terms. The beginning and end dates of the terms are different each year, depending on interactions with community holidays and other events. The school year may be described as a temporal aggregate whose parts are the four terms. A summary of the description is shown in .

Victorian school year 2020 — TemporalAggregate describing the school year in Victoria, Australia for 2020

This is encoded using the new elements as follows (incomplete):

ex:VicSchoolTerms2020
  a time:TemporalAggregate ;
  rdfs:label "Public school year - Victoria 2020 " ;
  time:hasBeginning ex:t1b ;
  time:hasEnd ex:t4e ;
  time:hasPart ex:t1 ;
  time:hasPart ex:t2 ;
  time:hasPart ex:t3 ;
  time:hasPart ex:t4 ;
.
ex:t1
  a time:ProperInterval ;
  rdfs:label "2020 Term 1" ;
  time:hasBeginning ex:t1b ;
  time:hasEnd ex:t1e ;
.
ex:t1b
  a time:Instant ;
  rdfs:label "2020 Term 1 begin" ;
  time:inXSDDate "2020-01-29"^^xsd:date ;
.
ex:t1e
  a time:Instant ;
  rdfs:label "2020 Term 1 end" ;
  time:inXSDDate "2020-03-17"^^xsd:date ;
.
ex:t2
  a time:ProperInterval ;
  rdfs:label "2020 Term 2" ;
  time:hasBeginning ex:t2b ;
  time:hasEnd ex:t2e ;
  time:intervalAfter ex:t1 ;
.
[...]

A JSON-LD representation of this data is also available for inspection.