We believe that Fred put down the apple. It is improbable that Greg is a rhino. There is a better than even chance that John took the football. It is highly unlikely that if either 'Fred put down the apple' or 'Greg is a rhino' but not both then Mary went to the office. It is probable that if either 'John took the football' or 'Fred put down the apple' but not both then Brian is green. We believe that if either 'Fred put down the apple' or 'John took the football' but not both then Bernhard is a lion.
There is a better than even chance that 'John took the football' or 'Greg is a rhino' or both.
There is a better than even chance that 'John took the football' or 'Greg is a rhino' or both.
There is almost no chance that 'John took the football' or 'Greg is a rhino' or both.

  and(A,B) :- A,B.
  or(A,B) :- A;B.
  nand(A,B) :- not(and(A,B)).
  nor(A,B) :- not(or(A,B)).
  xor(A,B) :- or(A,B), nand(A,B).

  %hop0
  0.75::factA.
  0.1::factB.
  0.6::factC.
  %hop1
  0.05::factX:-xor(factA,factB).
  0.7::factY:-xor(factC,factA).
  0.75::factZ:-xor(factA,factC).

  %hop2
  conclusion:-or(factC,factB).

  query(conclusion).
  
'John took the football' or 'Greg is a rhino' or both.