The Formal Syntax of Algernon

  

Notation: The italic font is used for non-terminals and the teletype font is used for terminals, (i.e., strings that actually occur in Algernon code).

[x]

denotes zero or one appearance of x.

x

denotes zero or more repetitions of x.

x

denotes one or more repetitions of x.

 atomic-formula  = (sterm fterm vterm  )    (not (sterm fterm vterm  ))

 fterm   		= 		 variable    frame    (sterm fterm)    (:slot slot)

 sterm   		= 		 variable    slot

 vterm   		= 		 fterm    number    string    (:quote expression)    (quote expression)

 domain   = Eframe    :number    :string    :symbol     :list

 path =  (form  ) plus access path restriction on variables.

 rule             		= 		(form   <- form  )   

                          				(form   -> form  )

 vars   = Evariable    (variable  )

 form             = Eatomic-formula   

     				(:taxonomy set-descriptor)

     				(:slot symbol (domain  ) slot-descriptor  )   

     				(:rules  fterm rule  )   

     				(:srules fterm rule  )   

     				(:eval expression)   

     				(:test expression)   

     				(:boundp variable)   

     				(:unboundp variable)   

     				(:bind variable expression)   

     				(:branch variable expression)   

     				(:funcall function expression  )   

     				(:a    vars . path)   

     				(:forc vars . path)   

     				(:the  vars . path)   

     				(:any  . path)   

     				(:cut  . path)   

     				(:db  atomic-formula)   

     				(:retrieve atomic-formula)   

     				(:unp  . path)   

     				(:fail . path)   

     				(:assume atomic-formula)   

     				(:neq fterm fterm)   

     				(:or   path  )   

     				(:all-paths path path)   

     				(:delete atomic-formula)   

     				(:clear-slot fterm slot)   

     				(:del-rule fterm rule)   

     				(:del-srule fterm rule)   

     				(:del-rules fterm slot)   

     				(:del-srules fterm slot)   

     				(:ask atomic-formula)   

     				(:show fterm)   

     				(:w-contra-positive . path)   

     				(:wo-contra-positive . path)   

     				(:no-completion form)

 slot-descriptor  = T:cardinality number   

     				:backlink slot   

     				:inverse slot   

     				:comment string

 set-descriptor  = (fterm set-descriptor   fterm  )

 expression  = Any Lisp expression   

                   				 (:values frame slot)   

                   				 (:non-values frame slot)

 variable  = a Lisp symbol whose print name begins with ``?''.

 frame     		= 		 a Lisp symbol that represents a frame in the knowledge-base.

 slot      		= 		 a Lisp symbol declared as a slot in the knowledge-base.

 number    		= 		 a Lisp number.

 string    		= 		 a Lisp string.

 symbol    		= 		 a Lisp symbol.

 function  		= 		 a Lisp function (in a form suitable to be passed to the Lisp
function funcall).