Used to extend class or slot definitions. For example, if we have a core schema where a gene has two slots for identifier and symbol, and we have a specialized schema for my_organism where we wish to add a slot systematic_name, we can avoid subclassing by defining a class gene_my_organism, adding the slot to this class, and then adding an apply_to pointing to the gene class. The new slot will be 'injected into' the gene class.
Domain and Range
- is_a: apply_to