It is probable that John left the milk. It is improbable that Greg is white. There is almost no chance that Jessica is a sheep. It is unlikely that if 'Greg is white and Jessica is a sheep' then Jason is tired. It is highly likely that if either 'Greg is white' or 'John left the milk' but not both then Brian is a rhino. It is unlikely that if 'Greg is white and Jessica is a sheep' then Mary took the football.
It is improbable that 'Mary took the football' or 'Brian is a rhino' or both.
There is a better than even chance that 'Mary took the football' or 'Brian is a rhino' or both.
It is improbable that 'Mary took the football' or 'Brian 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
  0.7::factA.
  0.1::factB.
  0.02::factC.
  %hop1
  0.2::factX:-and(factB,factC).
  0.9::factY:-xor(factB,factA).
  0.2::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Mary took the football' or 'Brian is a rhino' or both.