Ordinary atoms have values, and it is often convenient to imagine that an ordinary atom has several values. This can be accomplished by making a list of these values and using this list as the value whose elements are the desired several values. Frequently, however, these multiple values are used to encode properties. This is so common that LISP provides special features to accommodate properties .
Abstractly, a property is a function. LISP only provides for properties that apply to ordinary atoms and whose values are S-expressions, and it establishes and uses a special set of ...
