There is a better than even chance that Jessica is a sheep. It is highly likely that Sandra dropped the milk. It is probable that Winona is a wolf. It is unlikely that if 'Sandra dropped the milk and Winona is a wolf' then Mary grabbed the apple. It is highly unlikely that if either 'Winona is a wolf' or 'Jessica is a sheep' but not both then Greg is a swan. It is unlikely that if either 'Jessica is a sheep' or 'Sandra dropped the milk' but not both then John moved to the office.
There is little chance that 'John moved to the office' or 'Winona is a wolf' or both.
We believe that 'John moved to the office' or 'Winona is a wolf' or both.
There is little chance that 'John moved to the office' or 'Winona is a wolf' 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
  0.6::factA.
  0.9::factB.
  0.7::factC.
  %hop1
  0.2::factX:-and(factB,factC).
  0.05::factY:-xor(factC,factA).
  0.2::factZ:-xor(factA,factB).

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

  query(conclusion).
  
'John moved to the office' or 'Winona is a wolf' or both.