It is highly unlikely that Mary went to the kitchen. Chances are about even that Gertrude is a mouse. There is a better than even chance that Sandra took the football. Chances are about even that if 'Sandra took the football' or 'Gertrude is a mouse' or both then Bernhard is a frog. We doubt that if 'Sandra took the football and Mary went to the kitchen' then Greg is white. It is impossible that if either 'Gertrude is a mouse' or 'Mary went to the kitchen' but not both then Jessica is a sheep.
It is impossible that 'Jessica is a sheep and Greg is white'.
It is impossible that 'Jessica is a sheep and Greg is white'.
It is likely that 'Jessica is a sheep and Greg is white'.

  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
  0.05::factA.
  0.5::factB.
  0.6::factC.
  %hop1
  0.5::factX:-or(factC,factB).
  0.2::factY:-and(factC,factA).
  0.0::factZ:-xor(factB,factA).

  %hop2
  conclusion:-and(factZ,factY).

  query(conclusion).
  
'Jessica is a sheep and Greg is white'.