A frame can be considered just a convenient way to represent a set of predicates applied to constant symbols (e.g. ground instances of predicates.). For example, the frame above could be written:
sex(Adam,Male) spouse(Adam,Beth) child(Adam,Charles) child(Adam,Donna) child(Adam,Ellen)
More generally, the ground predicate
r(f,g) is represented, in a frame based system, by placing the value g in
the r slot of the frame f [Hayes, 1979]:
r(f,g) 
Throughout this document we use the teletype
font for Algernon statements and the italic font for predicate
calculus. We use standard predicate calculus notation except that we
find it convenient to use 
in addition to the usual
.