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 .