OWL 2 RL: nominals/ ObjectOneOf in SuperClasses

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Dear OWL 2 RL Working Group,

According to syntactic restriction of OWL 2 RL [1],
nominals/ObjectOneOfare not allowed in SuperClass
Expressions. However, allowing ObjectOneOf that contains exactly one
individual in SuperClas Expressions does not increase reasoning complexity.
The reason is that  SubClassOf axioms, which have such ObjectOneOf in
SuperClass
Expressions can be simulated in OWL 2 RL as follows:

SubClassOf(a:SubClassExpression, ObjectOneOf(a:Individual)), where
a:SubClassExpression is a SubClass Expression described in Table 2 of the
profile specification [1] and a:Individual is a named individual, can be
simulated by following OWL 2 RL axioms:

ClassAssertion( a:Individual, a:ClassA ) (1)

SubClassOf( a:SubClassExpression, a:ClassA ) (2)

SubClassOf( a:ClassA,

                      ObjectHasValue( a:hasRelation, a:AnotherIndividual )
) (3)

SubClassOf( ObjectOneOf( a:AnotherIndividual ),

                      ObjectMaxCardinality( 1 ObjectIverseOf
(a:hasRelation)  a:ClassA ) ) (4)

Intuitively, (3) and (4) entail that a:ClassA has at most one instance. In
addition, from (1) we know a:Individual is an instance of a:ClassA.
Therefore, a:ClassA has only one instance. Thus, we can derive:

                       SubClassOf( a:ClassA , ObjectOneOf( a:Individual ) )
 (5)

>From (2) and (5), we have:

                      SubClassOf( a:SubClassExpression, ObjectOneOf(
a:Individual ) )

Although ObjectOneOf that has exactly one individual might not be as widely
used as other axioms, it is still useful for ontology modelers. I would
like to ask if there is any good reason to disallow such ObjectOneOf
in SuperClass
Expressions ?

[1] http://www.w3.org/TR/owl2-profiles/#OWL_2_RL_2

Best regards,
Kien Tran
*

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Trung-Kien TRAN

Institute of Artificial Intelligence
University of Ulm
Tel: +49 (0)151 26 21 18 95
Homepage: http://www.uni-ulm.de/en/in/ki/staff/trung-kien-tran.html
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