existence_intervals

Existence Intervals

This example demonstrates various ontologies' representations of the period of time in which a thing exists. Some effort is put into describing differences in representing the existence of endurants vs. perdurants.

Take as an example a thing---and the thing might be endurant, perdurant, physical, cyber, thought, event, etc.---that exists starting at a time t0 and ceases to exist at a time t1. In the illustrations below, the start will be labeled t0, the end t1, the interval bounded by start and end i, the thing t.

The starting time of this thing is 2020-01-02T03:04:05.6789Z. The ending time of this thing is 2021-02-03T04:05:06.7890Z. Each illustration goes as far as it can with concepts in the referenced ontology to eventually tie the thing t to these timestamp-literals. Where available, reified "instant" objects will be favored over literal-valued properties.

This suggests a mapping table:

Example class or triple	Corresponding class or triple
ex:TimeBoundedThing	...
ex:ExistenceInterval	...
ex:Instant	...
kb:T ex:hasExistenceInterval kb:E	...
kb:T ex:existsAtAndSince kb:T0	...
kb:T ex:existsUntil kb:T1	...
kb:T ex:hasCreationTimestamp "2020-..."^^xsd:dateTime	...
kb:T ex:hasTerminationTimestamp "2021-..."^^xsd:dateTime	...
kb:E ex:hasStart kb:T0	...
kb:E ex:hasEnd kb:T1	...
kb:E ex:hasBeginningTimestamp "2020-..."^^xsd:dateTime	...
kb:E ex:hasEndingTimestamp "2021-..."^^xsd:dateTime	...
kb:T0 ex:hasTimestamp "2020-..."^^xsd:dateTime	...
kb:T1 ex:hasTimestamp "2021-..."^^xsd:dateTime	...

The mapping table is filled in for the various ontologies below with:

• Corresponding statements (class IRIs or full triples);
• "N/A", for not-available when a concept is known to not be mappable now, typically because no corresponding class or property is currently defined; and
• "TBD", when a design decision can be taken, typically because of a potential class- or property-equality declaration.

Note that "N/A" does not mean that a mapping is not possible. It only means that classes and properties are not defined at the present moment.

UCO 1.3.0

UCO declares two property-pairs setting time boundaries:

• core:startTime and core:endTime, used to bound core:Events and core:Relationships.
• action:startTime and action:endTime, used to bound action:Actions.

The following table shows the time coverage for the three UCO classes that currently encode constraints on time properties:

UCO Class	Figure
uco-action:Action
uco-core:Event
uco-core:Relationship

The mapping for uco-action:Action would be as follows.

Example class or triple	Corresponding class or triple
ex:TimeBoundedThing	uco-action:Action
ex:ExistenceInterval	TBD
ex:Instant	N/A
kb:T ex:hasExistenceInterval kb:E	TBD
kb:T ex:existsAtAndSince kb:T0	N/A
kb:T ex:existsUntil kb:T1	N/A
kb:T ex:hasCreationTimestamp "2020-..."^^xsd:dateTime	kb:T uco-action:startTime "2020-..."^^xsd:dateTime
kb:T ex:hasTerminationTimestamp "2021-..."^^xsd:dateTime	kb:T uco-action:endTime "2021-..."^^xsd:dateTime
kb:E ex:hasStart kb:T0	N/A
kb:E ex:hasEnd kb:T1	N/A
kb:E ex:hasBeginningTimestamp "2020-..."^^xsd:dateTime	TBD
kb:E ex:hasEndingTimestamp "2021-..."^^xsd:dateTime	TBD
kb:T0 ex:hasTimestamp "2020-..."^^xsd:dateTime	N/A
kb:T1 ex:hasTimestamp "2021-..."^^xsd:dateTime	N/A

uco-core:Event and uco-core:Relationship will look similar.

The "TBD"s above pertain to a decision UCO can make on how endurants and perdurants relate to time, under discussion UCO Issue 544.

OWL-Time

OWL-Time provides the class time:TemporalEntity. Guidance offers options on how to relate time-things (time:TemporalEntity) to things that exist in time (like an activity or an object), drawn from Section 3.1.

The properties :hasTemporalDuration, :hasBeginning and :hasEnd, together with a fourth generic property :hasTime, support the association of temporal information with any temporal entity, such as an activity or event, or other entity. These provide a standard way to attach time information to things, which may be used directly in applications if suitable, or specialized if needed.

The following figure shows the time coverage for the general usage of time:TemporalEntity:

The mapping for time:TemporalEntity would be as follows.

Example class or triple	Corresponding class or triple
ex:TimeBoundedThing	owl:Thing
ex:ExistenceInterval	time:TemporalEntity
ex:Instant	time:Instant
kb:T ex:hasExistenceInterval kb:E	kb:T time:hasTime kb:E
kb:T ex:existsAtAndSince kb:T0	N/A
kb:T ex:existsUntil kb:T1	N/A
kb:T ex:hasCreationTimestamp "2020-..."^^xsd:dateTime	N/A
kb:T ex:hasTerminationTimestamp "2021-..."^^xsd:dateTime	N/A
kb:E ex:hasStart kb:T0	kb:E time:hasBeginning kb:T0
kb:E ex:hasEnd kb:T1	kb:E time:hasEnd kb:T1
kb:E ex:hasBeginningTimestamp "2020-..."^^xsd:dateTime	N/A
kb:E ex:hasEndingTimestamp "2021-..."^^xsd:dateTime	N/A
kb:T0 ex:hasTimestamp "2020-..."^^xsd:dateTime	kb:T0 time:inXSDDateTime "2020-..."^^xsd:dateTime
kb:T1 ex:hasTimestamp "2021-..."^^xsd:dateTime	kb:T1 time:inXSDDateTime "2021-..."^^xsd:dateTime

Some of the examples in the OWL-TIME specification include demonstrations of time:TemporalEntity that allow for endurants and perdurants as direct subclasses. Note that the examples section is non-normative.

• 5.4, "iCalendar" instantiates the endurant "Abraham Lincoln" (node _:TE-2).
• 5.6, "A Use Case for Scheduling" instantiates perdurants some teleconference and some meeting (nodes ex:telecon and ex:meeting, respectively).
• 5.7, "Alignment of PROV-O with OWL-Time" states that prov:Activity and prov:InstantaneousEvent can be subclasses of time:TemporalEntity and time:Instant, respectively.