I am going through some questions on RDFS/OWL models, and have to infer some triples based on a model. However, I haven't seen the restriction in this model, at least a restriction written like this.
:John :worksAt :companyA
:John rdf:type :employee
:John rdf:type [∃⩽1 owl:onProperty :worksAt]
My understanding of this is along the lines of "An employee must have at least one :worksAt", or in other words owl:minCardinality of 1.