Requesting Information from the User

The Lisp interface special forms make it easy to define functions for interacting with the user to request information for the Algernon knowledge base.

This section presents a simple user interface, intended to illustrate the basic method and encourage you to implement your own more sophisticated interface, tailored to the needs of your application.

This interface defines sets of slots associated with rules that invoke a Lisp function appropriate to that type of slot, to interact with the user.

• User-ask-slots are slots that automatically request information from the user if it is not already known. We have two categories at the moment: those that take Boolean values and those that take numerical values.

    (tell '((:taxonomy (Slots
                        (User-Ask-Slot
                         (Boolean-Ask-Slots)
                         (Numerical-Ask-Slots))))))

• Boolean ask-slots have rules (declared with :srules since they are accessed from the slot in a query or assertion) that call the CommonLisp function y-or-n-p to determine whether the user knows the truth of a given predicate.

    (tell '((:srules Boolean-Ask-Slots
             ((?p ?x true)
              <-
              (:test (y-or-n-p "Is it known that ~((~a ~a true)~)?" '?p '?x))))))

• Boolean ask-slots also have a set of forward-chaining rules to fill out the various equivalent ways a truth value can be known. (This is clearly redundant. Is it unacceptable? Should truth values have a canonical representation? Hard to say.)

    (tell '((:srules Boolean-Ask-Slots
             ((?p ?x true)        -> (not (?p ?x false)))
             ((?p ?x false)       -> (not (?p ?x true)))
             ((not (?p ?x true))  -> (?p ?x false))
             ((not (?p ?x false)) -> (?p ?x true)))))

• Numerical-valued ask-slots get their values by calling a function named ask-numerical-value-for. Its code is provided in the Algernon example file lisp-interface.lisp. The user is requested to provide a value. By using the :branch special form, the rule can fail if the user refuses to provide a value.

    (tell '((:srules Numerical-Ask-Slots
             ((?p ?f ?v)
              <-
              (:branch ?v (ask-numerical-value-for '?v '(?p ?f ?v)))))))

• There is also a function named select-option in the Algernon example file lisp-interface.lisp. It allows Algernon to present the user with a menu of options.

We demonstrate these features with some more interaction regarding Adam's family. We assert that the slots friendly and age belong to sets that will allow them to inherit the interaction rules above.

  (tell '((isa (:slot friendly) Boolean-Ask-Slots)
          (isa (:slot age)      Numerical-Ask-Slots)))

For each of Adam's children, we query whether he or she is friendly. If this is known, we report the result. This is similar to a previous interaction, but specified on a rule inherited from a set.

  (ask '((child Adam ?kid)
         (friendly ?kid ?tv)
         (:eval (format t "~%Is Adam's child ~a friendly?  ~a." '?kid '?tv)))
       :comment "Ask the user to provide a truth value.")

QUERYING:  Ask the user to provide a truth value.
Is it known that (friendly ellen true)? (Y or N): y
Is it known that (friendly donna true)? (Y or N): n
Is it known that (friendly charles true)? (Y or N): y

Is Adam's child ELLEN friendly?  TRUE.
Is Adam's child CHARLES friendly?  TRUE.

 Result (1 of 2):
   Bindings:            ?tv    --- true "[true]"
                        ?kid   --- ellen "[ellen]"
                       
 Result (2 of 2):
   Bindings:            ?tv    --- true "[true]"
                        ?kid   --- charles "[charles]"
                       
  => T

Next, for each child, ask the user for the child's age. Any non-numerical value counts as refusal to answer, so the rule and the attempt to query (age ?kid ?n) fail.

  (ask '((child Adam ?kid)
         (age ?kid ?n)
         (:eval (format t "~%~a's age is ~a." '?kid '?n)))
       :comment "Ask the user to provide a numerical value.")

QUERYING:  Ask the user to provide a numerical value.

Please give me a numerical value for ?n in (age ellen ?n):  12

Please give me a numerical value for ?n in (age donna ?n):  no

Please give me a numerical value for ?n in (age charles ?n):  16

ELLEN's age is 12.
CHARLES's age is 16.

 Result (1 of 2):
   Bindings:            ?n     --- 12
                        ?kid   --- ellen "[ellen]"
                       
 Result (2 of 2):
   Bindings:            ?n     --- 16
                        ?kid   --- charles "[charles]"
                       
  => T

Finally, we ask the user to select one of a list of options.

  
  (ask '((:eval (format t "~%Which kid is your favorite?"))
         (:bind ?options (:values Adam child))
         (:branch ?choice (select-option '?options ))
         (:eval (format t "~%You picked ~a." '?choice)))
       :comment "Ask the user to pick one of a given set of options.")

QUERYING:  Ask the user to pick one of a given set of options.

Which kid is your favorite?

+------------------------------
| Select one (`0' for none)
+------------------------------
|   1:   ELLEN
|   2:   DONNA
|   3:   CHARLES
+------------------------------
| Select item number (1 to 3):  1

You picked ELLEN.

 Result:
   Bindings:            ?choice   --- ellen "[ellen]"
                        ?options   --- (ellen "[ellen]" donna "[donna]" charles "[charles]")
                       
  => T