OWL-Time [owl-time] is an ontology for temporal entities, with a particular focus on the description of
relations between time intervals.
However, there are certain relations between more general temporal entities (in particular, time instants) that
cannot be expressed using the 15 interval relations defined in OWL-Time.
This note adds four new relations: time:equals, time:hasInside, time:disjoint and
time:notDisjoint which complement the original relations and allow for description of more
relationships between 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 with these extensions is available here.
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New properties are introduced in this extension to OWL-Time.
The new elements concern relationships between temporal entities which cannot be easily expressed through
combination of the predicates provided in OWL-Time using the axiomatization available in OWL2.
The ontology document <owl:imports> the 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.
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described in the
charter.
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 basic relationships that were identified by Allen:
Between general temporal entities: time:before, time:after
A summary of the semantics of the intervals relationships is shown in Figure 1.
Figure 1 Allen's relations between temporal intervals. Figure from [owl-time].
In principle, any relationship between temporal entities can be built up through logical combination of
members of these primitive relations.
However, in practice, there are limitations in the expressivity of the RDF implementation of OWL2
[owl2-direct-semantics][owl2-rdf-based-semantics], particularly around unions and complements of properties.
Furthermore most of the relationships are only defined for proper-intervals - i.e. temporal entities of non-zero
duration - which cannot be used for relationships involving time instants.
These considerations mean that it is convenient to introduce a small set of additional relations
explicitly, in order to support some applications more efficiently.
Two were already included in OWL-Time:
time:intervalIn is the the union of
time:intervalDuring, time:intervalStarts,and time:intervalFinishes;
time:intervalDisjoint is the the union of
time:intervalBefore, and time:intervalAfter
Note that in OWL2 the union of properties can only be approximated through a set of sub-property axioms, which
link the members up to the union, but does not exclude the possibility of other sub-properties being added to the
union.
1.2 New temporal relations
This note defines a further four relations, all scoped to general temporal entities (i.e. not restricted to either
intervals or instants):
time:disjoint is the union of
time:before, time:after, and time:intervalDisjoint;
time:equals is the super-property of
time:intervalEquals, but is not restricted to relations between proper intervals;
time:hasInside is the union of
time:inside, time:intervalContains, time:intervalStartedBy,and
time:intervalFinishedBy;
time:notDisjoint is the union of
time:equals, time:hasInside, time:intervalIn,
time:intervalMeets, time:intervalMetBy, time:intervalOverlaps,
time:intervalOverlappedBy,
which is the complement of time:disjoint
A graph showing the full set of 22 relations between temporal entitites is provided in Figure 2.
Figure 2 All relations between temporal entities, shown as a graph with sub-property, inverse, and disjoint relationships
2. Notation and namespaces
Classes and properties from the 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
ex
http://example.org/ssn/
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.
If a temporal entity T1 is disjoint with another temporal entity T2, then the beginning of T1 is after
the end of T2, or the end of T1 is before the beginning of T2, i.e. the two entities
do not overlap or coincide in any way, but their ordering relationship is not known.
If a temporal entity T1 equals another temporal entity T2, then the beginning of T1 is coincident with
the beginning of T2, and the end of T1 is coincident with the end of T2, and the beginning of T1 may be
coincident with the end of T1.
If a temporal entity T1 hasInside it another temporal entity T2, then the beginning of T1 is
coincident with or before the beginning of T2, and the end of T1 is concident with or after the end of
T2, except that end of T1 may not be coincident with the end of T2 if the beginning of T1 is coincident
with the beginning of T2.
If a temporal entity T1 is notDisjoint with another temporal entity T2, then the the two entities
overlap or coincide in some way, but their ordering relationship is not known. This relation is the
complement of disjoint and is the union of equals, hasInside, in, meets, metBy, overlaps, overlappedBy.
Jack's wedding concides with Abby's birthday in 2020.
You can't sleep and eat at the same time, but you could take a nap in the morning or afternoon.
A quiz will occur at some point during the class - it could be at the beginning, middle or end.
6. IANA Considerations
The link relation types below are proposed to be registered by IANA per Section 6.2.1 of [RFC8288]:
6.1 timeDisjoint Link Relation Type
Relation name
timeDisjoint
Description
refers to a resource associated with a time entity that begins after the end of the time entity associated with the context resource, or ends before the beginning of the time entity associated with the context resource, i.e. the two entities do not overlap or coincide in any way, but their ordering relationship is not known.
refers to a resource associated with a time entity that begins at the beginning of the time entity associated with the context resource, and ends at the end of the time entity associated with the context resource, i.e. the two entities coincide temporally. The beginning and end may coincide.
refers to a resource associated with a time entity that begins after or coincident with the beginning of the time entity associated with the context resource, and ends before or coincident with the end of the time entity associated with the context resource, except that the end may not be coincident with the end of the context resource if the beginning is coincident with the beginning of the context resource.
refers to a resource associated with a time entity that overlaps or coincides with the time entity associated with the context resource in some way, but their ordering relationship is not known.
