$PRED ===== Syntax: ($PRED <predication>) or [<predication>] with: <predication> ::= {<compound-predication> | <simple-predication> | (match <bql-variable> {bab-lisp-expr. | <bql-variable>} | (element-of <bql-variable> {<bab-lisp-expr.> | <bql-variable>} | <lisp-type: T>} PREDICATIONS are statements about the knowledge in the knowledge base. They are characterized with brackets. A simple-predication consists of a name and one or two arguments. If the predication only has one argument, then it is called a one-argument predication, otherwise a two-argument predication. If predications are combined, the resulting construct is called a compound predication. A ONE-ARGUMENT-PREDICATION describes a frame-instance relation. A TWO-ARGUMENT-PREDICATION describes a relation between an instance and a value and is used in connection with tell, untell and retell. A COMPOUND-PREDICATION is a set of SIMPLE PREDICATIONs bound with [AND, [OR or [NOT. The expressions of the predications will be worked out from left to right. Example: >(ask [city _city] (kb-format "~% ~A" _city)) #<CAPITAL-CITY PARIS> #<CITY WUPPERTAL> #<CAPITAL-CITY LONDON> #<CITY DEN-HAAG> #<CAPITAL-CITY AMSTERDAM> NIL