Extensions to the OWL-Time Ontology - temporal aggregates

W3C Interest Group Note

This version:
Latest published version:
Latest editor's draft:
Simon Cox (CSIRO)
Adam Shepherd
Charles Vardeman II
GitHub w3c/sdw
File a bug
Commit history
Pull requests
OGC Document Number:
OGC 20-022


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:

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].

3. Conformance

As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.

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):

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

A. Acknowledgements

The editors would like to thank the members of the ESIP Semantic Technologies Committee for their contributions during the development of this document.

B. References

B.1 Normative references

OWL 2 Web Ontology Language Manchester Syntax (Second Edition). Matthew Horridge; Peter Patel-Schneider. W3C. 11 December 2012. W3C Note. URL: https://www.w3.org/TR/owl2-manchester-syntax/
RDF 1.1 Turtle. Eric Prud'hommeaux; Gavin Carothers. W3C. 25 February 2014. W3C Recommendation. URL: https://www.w3.org/TR/turtle/

B.2 Informative references

Actions and events in interval temporal logic In: Spatial and Temporal Reasoning. O. Stock, ed., Kluwer, Dordrecht, Netherlands, pp. 205-245.. J.F. Allen; G. Ferguson. 1997. URL: http://dx.doi.org/10.1007/978-0-585-28322-7_7
Towards a general theory of action and time. Artificial Intelligence 23, pp. 123-154.. J.F. Allen. 1984. URL: http://dx.doi.org/10.1016/0004-3702%2884%2990008-0
CURIE Syntax 1.0. Mark Birbeck; Shane McCarron. W3C. 16 December 2010. W3C Note. URL: https://www.w3.org/TR/curie/
Time Ontology in OWL. Simon Cox; Chris Little. W3C. 26 March 2020. W3C Candidate Recommendation. URL: https://www.w3.org/TR/owl-time/