There is a very good chance that Greg is a lion. There is little chance that Bernhard is a swan. It is probably not the case that Brian is yellow. It is highly unlikely that if 'Brian is yellow and Bernhard is a swan' then Sandra left the football. We doubt that if either 'Greg is a lion' or 'Brian is yellow' but not both then John went to the garden. We believe that if 'Brian is yellow and Bernhard is a swan' then Julius is a rhino.
It is likely that 'Sandra left the football and Greg is a lion'.
It is impossible that 'Sandra left the football and Greg is a lion'.
It is likely that 'Sandra left the football and Greg is a lion'.

  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.
  0.1::factB.
  0.25::factC.
  %hop1
  0.05::factX:-and(factC,factB).
  0.2::factY:-xor(factA,factC).
  0.75::factZ:-and(factC,factB).

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

  query(conclusion).
  
'Sandra left the football and Greg is a lion'.