Type comparators enable us to specify constraints on some types in a query: strict specialization (<:), specialization or same type (<=:), same type (=:), generalization or same type (>=:), strict generalization (>:). These operators can also be combined with a ! negation operator (!<:, !<=:, etc.).
For instance, by using the <: operator in the following example, we constrain the document to be a strict specialization of a thesis (e.g. a PhD thesis, a MSc thesis, etc.).
?doc <: kmp:Thesis
The following example excludes students and their sub-types.
?p rdf:type kmp:Person ?p !<=: kmp:Student