The ConstraintNode type is provided to support usecases in which a node in a structured data graph is described with properties which appear to describe a single entity, but are being used in a situation where they serve a more abstract purpose. A ConstraintNode can be described using constraintProperty and numConstraints. These constraint properties can serve a

variety of purposes, and their values may sometimes be understood to indicate sets of possible values rather than single, exact and specific values.