86 CHAPTER 4 Types of rules 4.9.1.1.2 Formal extensional definitions A formal extensional definition defines the subject business term by using an extensional definition: one that lists a complete set of hyponyms (terms that refer to subsets of the set referred to by the original term): for example, R72. An immediate family member of a person is by definition a parent, sibling, spouse, or child of that person. 4.9.1.1.3 Symbolic literal definitions A symbolic literal definition defines the subject business term using one or more literals: for example, R73. End of financial year is by definition June 30. 19 R74. A calendar year is by definition 365 days or 366 days from a January 1 to the following December 31. 4.9.1.2 Categorization scheme enumerations