The SWRL temporal built-in "temporal:equals" doesn't work as expected

[Ines-Akaichi]

I am using the SWRL temporal built-ins provided in [1] to compare dateTime values. I am mainly interested in the following operators: equals, before, after.

"before" and "after" work for me given the example below. However, my issue is when using "equals".

For example, I have the following RDF:

@prefix : <http://example.org/test#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix ex: <http://example.org#> .

:elapse1    :hasTime   "2026-01-11T17:30:00"^^xsd:dateTime .

:elapse2    :hasTime   "2026-01-11T17:30:00"^^xsd:dateTime .

:elapse3    :hasTime   "2026-01-11T11:30:00"^^xsd:dateTime .

:BeforeEvent rdf:type owl:Class .
:AfterEvent rdf:type owl:Class .
:Equals rdf:type owl:Class . 

:hasTime a owl:DatatypeProperty ;
        rdfs:range xsd:dateTime .

I also have the following SWRL rules:

  :hasTime (?e1,?t1) ^ :hasTime (?e2,?t2) ^ temporal:before(?t1,?t2) -> :BeforeEvent(?e1)

   :hasTime (?e1,?t1) ^ :hasTime (?e2,?t2) ^ temporal:after(?t1,?t2) -> :AfterEvent(?e1)

   :hasTime (?e1,?t1) ^ :hasTime (?e2,?t2) ^ temporal:equals(?t2,?t1) -> :Equals(?e2)

I run these rules using the SWRLTab in Protege 5.6.7

The result shows me the following:

:elapse1 a :AfterEvent, :Equals .
:elapse2 a :AfterEvent, :Equals .
:elapse3 a :BeforeEvent, :Equals .               

I understand that :elapse1 and :elapse2 are of type :AfterEvent. I also understand that :elapse3 is of type :BeforeEvent. What I don't understand is why :elapse1, :elapse2, and :elapse3 are of type Equals. Specifically :elapse3 is different from :elapse1 and :elapse2. I expected that only both :elapse1 and :elapse2 are of type :Equals.

Anyone has an explanation for this behavior?

Thanks a lot!

[martinjoconnor]

Can you verify that you are using the latest 2.1.3 SWRLTab Plugin in Protege.

Go to File -> Check for plugins... to check for the currently installed version and updated if needed.

[martinjoconnor]

The behavior you observed is a consequence of OWL semantics, not an issue with the temporal built-ins. OWL follows the Open World Assumption and does not adopt the Unique Name Assumption, so different IRIs are not assumed to denote different individuals unless this is explicitly stated. In addition, SWRL allows the same individual to be bound to multiple variables in a rule. As a result, your rule permits the binding where ?e1 and ?e2 refer to the same individual, making temporal:equals(?t1, ?t2) trivially true because a time value always equals itself. Since the ontology does not entail that the events are distinct, the reasoner cannot exclude this self-binding, and every event with a hasTime value ends up classified as :Equals. To achieve the intended behavior, you must explicitly require individual distinctness using OWL’s differentFrom semantics, either via asserted owl:differentFrom axioms or by including differentFrom(?e1, ?e2) in the rule body.

Rule example

:hasTime(?e1,?t1) ^ :hasTime(?e2,?t2) ^ differentFrom(?e1,?e2) ^ temporal:equals(?t1,?t2) -> :Equals(?e1)

[Ines-Akaichi]

Dear Martin,

You are right! Adding individual distinctness solved the issue for me!
In my case, I added the individual distinctness directly in my turtle file.
thank you for your prompt answer!

Ines