It is probably the case that John took the football. It is unlikely that Bernhard is yellow. We doubt that Julius is gray. There is little chance that if either 'John took the football' or 'Bernhard is yellow' but not both then Sumit is thirsty. It is highly unlikely that if 'Bernhard is yellow' or 'John took the football' or both then Greg is a lion. There is almost no chance that if 'John took the football and Julius is gray' then Daniel left the milk.
It is impossible that 'Sumit is thirsty and Greg is a lion'.
It is impossible that 'Sumit is thirsty and Greg is a lion'.
We believe that 'Sumit is thirsty 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
  0.7::factA.
  0.2::factB.
  0.2::factC.
  %hop1
  0.1::factX:-xor(factA,factB).
  0.05::factY:-or(factB,factA).
  0.02::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Sumit is thirsty and Greg is a lion'.