A Simple Demonstration of the Basic Problem Solver Debugger

Introduction

KM: (ps-debug)
      ---------------------------------------------
      A debugger for the Basic Problem Solver v0.01
      ---------------------------------------------
(ps-debug)

An object is thrown from the top of a cliff.
The initial horizontal velocity of the object is 20 m/s.
The initial vertical velocity of the object is 0 m/s.
The height of the cliff is 125 m.
The object falls from the top of the cliff to the level ground.
What is the duration of the fall?

Snippet #1

KM(9): (load "question.triples")
T
KM(10): (ps-debug)
      ---------------------------------------------
      A debugger for the Basic Problem Solver v0.01
      ---------------------------------------------
(ps-debug) begin *scenario* *compute-questions*
Basic Problem Solver is reset.
---------------------------------------------------------
The following triples were contributed by the rule-engine
---------------------------------------------------------

(|_Velocity-Value189| |instance-of| |Velocity-Value|) 
(|_Velocity-Value189| |value| (:|pair| 0 |*meter-per-second|))
(|_Fall2331_c184| |velocity| |_Velocity-Value189|)

T
(ps-debug) next
Trying _Viewpoint191  => NIL
T
(ps-debug) continue
Unifying _Object2305_c274 with _Physical-Object240_c281.
Unifying _Fall2331_c270 with _Fall235_c283.
Unifying _Velocity-Value189_c267 with _Velocity-Value237_c286.
Unifying _Top2306_c277 with _Spatial-Entity239_c285.
Unifying _Ground2335_c269 with _Spatial-Entity238_c280.
Unifying _Duration2339_c268 with _Duration-Value241_c282.
Unifying NIL with NIL.
Unifying _Height2328_c271 with _Height-Value242_c284.
Trying _Viewpoint274  => (_Viewpoint274)
_Viewpoint274
(ps-debug) ls
-------------------
Viewpoint hierarchy
-------------------
_Viewpoint191
    _Viewpoint274
    _Viewpoint275 ...
    _Viewpoint276 ...
    _Viewpoint277 ...

--------------------------------------------------
Viewpoints were examined in the following sequence
--------------------------------------------------
(_Viewpoint191 _Viewpoint274)

T
(ps-debug) 

Snippet #2

KM(37): (load "question.triples")
T
KM(38): (ps-debug)
      ---------------------------------------------
      A debugger for the Basic Problem Solver v0.01
      ---------------------------------------------
(ps-debug) begin *scenario* *compute-questions*
Basic Problem Solver is reset.
---------------------------------------------------------
The following triples were contributed by the rule-engine
---------------------------------------------------------
(|_Velocity-Value1363| |instance-of| |Velocity-Value|)
(|_Velocity-Value1363| |value| (:|pair| 0 |*meter-per-second|))
(|_Fall2331_c2415| |velocity| |_Velocity-Value1363|)

T
(ps-debug) adhoc
Entering adhoc mode
(ps-debug) try Metal-Nonmetal-Reaction
NIL
(ps-debug) try all
_Viewpoint1449 is mapped to Fall-From-Rest-System
_Viewpoint1450 is mapped to Uniform-Acceleration-System
_Viewpoint1451 is mapped to Uniform-Motion-System
_Viewpoint1452 is mapped to Cell
T
(ps-debug) pick _Viewpoint1451
Unifying _Object2305_c2482 with _Physical-Object1398_c2488.
Unifying _Fall2331_c2478 with _Move1400_c2491.
Unifying _Velocity-Value1363_c2475 with _Velocity-Value1401_c2489.
Unifying _Duration2339_c2476 with _Duration-Value1402_c2490.
Picking _Viewpoint1451 as the next Viewpoint
_Viewpoint1451 has viewpoint-answer => (There is a duration.)
The current Viewpoint is _Viewpoint1451

(ps-debug) why
(
Equation-Set used          : Uniform-Motion-Equation-Set
Known variable bindings    : |v| = (0 (/ |*meter| |*second|))
Solved variable bindings   : Not appliable
Unsolved variable bindings : (|d| |t|)
Equation expressions       : (= |d| (* |v| |t|))

)
(ps-debug) unpick
The current Viewpoint is _Viewpoint1365.

(ps-debug) try all
_Viewpoint1541 is mapped to Fall-From-Rest-System
_Viewpoint1542 is mapped to Uniform-Acceleration-System
_Viewpoint1543 is mapped to Uniform-Motion-System
_Viewpoint1544 is mapped to Cell
T
(ps-debug) pick _Viewpoint1541
Unifying _Object2305_c2677 with _Physical-Object1507_c2684.
Unifying _Fall2331_c2673 with _Fall1502_c2686.
Unifying _Velocity-Value1363_c2670 with _Velocity-Value1504_c2689.
Unifying _Top2306_c2680 with _Spatial-Entity1506_c2688.
Unifying _Ground2335_c2672 with _Spatial-Entity1505_c2683.
Unifying _Duration2339_c2671 with _Duration-Value1508_c2685.
Unifying NIL with NIL.
Unifying _Height2328_c2674 with _Height-Value1509_c2687.
Picking _Viewpoint1541 as the next Viewpoint
_Viewpoint1541 has viewpoint-answer => (The duration of the fall = 5.05 second.)
The current Viewpoint is _Viewpoint1541

(ps-debug) why
(
Equation-Set used          : Fall-From-Rest-Equation-Set
Known variable bindings    : |g| = (9.8 (/ |*meter| (* |*second| |*second|)))
                           : |y| = (125 |*meter|)
Solved variable bindings   : |t| = (5.0507627 |*second|)
Unsolved variable bindings : (|v| |v0|)
Equation expressions       : (= |v| (+ |v0| (* |g| |t|)))
                           : (= |y| (* (* 0.5 |g|) (|expt| |t| 2)))
                           : (= |v| (|sqrt| (+ (|expt| |v0| 2) (* (* 2 |g|) |y|))))

)
(ps-debug) adhoc
Exiting adhoc mode

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