Chances are slight that Mary went to the bedroom. It is probably not the case that Brian is green. There is little chance that Winona is a mouse. It is likely that if either 'Winona is a mouse' or 'Brian is green' but not both then Fred discarded the apple. We believe that if 'Mary went to the bedroom and Winona is a mouse' then Greg is white. It is probably not the case that if 'Winona is a mouse' or 'Brian is green' or both then John took the football.
There is a very good chance that either 'Brian is green' or 'John took the football' but not both.
We doubt that either 'Brian is green' or 'John took the football' but not both.
There is a very good chance that either 'Brian is green' or 'John took the football' but not 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
  0.1::factA.
  0.25::factB.
  0.1::factC.
  %hop1
  0.7::factX:-xor(factC,factB).
  0.75::factY:-and(factA,factC).
  0.25::factZ:-or(factC,factB).

  %hop2
  conclusion:-xor(factB,factZ).

  query(conclusion).
  
Either 'Brian is green' or 'John took the football' but not both.