Extensions to the OWL-Time Ontology - temporal aggregates

W3C Interest Group Note 7 July 2020

This version:: https://www.w3.org/TR/2020/NOTE-vocab-owl-time-agg-20200707/
Latest published version:: https://www.w3.org/TR/vocab-owl-time-agg/
Latest editor's draft:: https://w3c.github.io/sdw/time-aggregates/
Editors:: Simon Cox (CSIRO); Adam Shepherd; Charles Vardeman II
Participate:: GitHub w3c/sdw; File a bug; Commit history; Pull requests
OGC Document Number:: OGC 20-022

Abstract

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.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

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.

This document was published by the Spatial Data on the Web Interest Group as an Interest Group Note.

GitHub Issues are preferred for discussion of this specification. Alternatively, you can send comments to our mailing list. Please send them to public-sdwig@w3.org (archives).

Publication as an Interest Group Note does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

The group does not expect this document to become a W3C Recommendation. The disclosure obligations of the Participants of this group are described in the charter.

This document is governed by the 1 March 2019 W3C Process Document.

1. Motivation and background

This section is non-normative.

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 Figure 1.

temporal aggregate — Figure 1 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.

2. 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].

4. Vocabulary specification

4.1 Classes

4.1.1 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`

4.2 Properties

4.2.1 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`

4.2.2 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`

5. Examples

This section is non-normative.

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

5.1 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 Figure 2.

Victorian school year 2020 — Figure 2 TemporalAggregate describing the school year in Victoria, Australia for 2020

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

Example 1: State of Victoria school year

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.