It is unlikely that Bernhard is gray. There is almost no chance that Greg is a lion. It is likely that John moved to the office. It is impossible that if 'Greg is a lion and Bernhard is gray' then Sandra took the football. It is highly unlikely that if 'Greg is a lion and Bernhard is gray' then Lily is a rhino. It is almost certain that if either 'John moved to the office' or 'Greg is a lion' but not both then Mary left the apple.
It is impossible that 'Greg is a lion and Bernhard is gray'.
It is impossible that 'Greg is a lion and Bernhard is gray'.
We believe that 'Greg is a lion and Bernhard is gray'.

  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
  0.2::factA.
  0.02::factB.
  0.7::factC.
  %hop1
  0.0::factX:-and(factB,factA).
  0.05::factY:-and(factB,factA).
  0.95::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'Greg is a lion and Bernhard is gray'.