Lisp provides for every symbol a property list that associates named properties with the symbol:

             binding
PRESIDENT ----------->  BUSH
|                      |
| DUTIES (CINC ...)    | WIFE --->   LAURA
|                      |              |
| ...                  | AGE  57      | ...

This mechanism has several advantages:

1. New properties can be added at any time; there is no need to pre-declare properties.

2. Only those properties needed for each individual object need to be stored.

3. A property can have a single value or a list of values associated with it.

Property lists are a natural mechanism to use in implementing semantic networks.

Contents    Page-10    Prev    Next    Page+10    Index