There is a very good chance that Bernhard is a swan. There is almost no chance that Mary went to the garden. There is little chance that John took the football. It is almost certain that if 'Bernhard is a swan' or 'John took the football' or both then Brian is white. It is impossible that if either 'Bernhard is a swan' or 'Mary went to the garden' but not both then Julius is a rhino. It is probably not the case that if 'Mary went to the garden' or 'Bernhard is a swan' or both then Greg is a lion.
It is unlikely that 'Greg is a lion and Brian is white'.
It is unlikely that 'Greg is a lion and Brian is white'.
It is probable that 'Greg is a lion and Brian 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
  0.8::factA.
  0.02::factB.
  0.1::factC.
  %hop1
  0.95::factX:-or(factA,factC).
  0.0::factY:-xor(factA,factB).
  0.25::factZ:-or(factB,factA).

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

  query(conclusion).
  
'Greg is a lion and Brian is white'.