By default, properties are multivalued, there are no restrictions in the number of values a property can store.
INSERT DATA { <cat> a ex:Mammal .
<dog> a ex:Mammal .
<peter> a ex:Mammal ;
ex:pets <cat>, <dog> }
Wherever this is not desirable, cardinality can be limited on properties through nrl:maxCardinality.
ex:cromosomes a rdf:Property;
rdfs:domain ex:Eukaryote;
rdfs:range xsd:integer;
nrl:maxCardinality 1.
This will raise an error if the SPARQL updates in the endpoint end up in the property inserted multiple times.
# This will fail
INSERT DATA { <cat> a ex:Mammal;
ex:cromosomes 38;
ex:cromosomes 42 }
# This will succeed
INSERT DATA { <donald> a ex:Mammal;
ex:cromosomes 47 }