'Constituent' should depend on some layering of the ontology. For example, scientific granularities or ontological 'strata' are typical layerings. A constituent is a part belonging to a lower layer. Since layering is actually a partition of the ontology, constituents are not properly classified as parts, although this kinship can be intuitive for common sense. Example of specific constant constituents are the entities constituting a setting (a situation), whilethe entities constituting a collection are examples of generic constant constituents.