It is highly likely that John put down the apple. We believe that Fred left the football. There is a very good chance that Brian is yellow. It is unlikely that if 'Fred left the football and Brian is yellow' then Sandra got the milk. It is impossible that if 'John put down the apple and Brian is yellow' then Greg is a rhino. It is unlikely that if either 'Brian is yellow' or 'Fred left the football' but not both then Julius is white.
It is highly unlikely that 'Greg is a rhino' or 'Julius is white' or both.
It is highly unlikely that 'Greg is a rhino' or 'Julius is white' or both.
It is almost certain that 'Greg is a rhino' or 'Julius is white' 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
  0.9::factA.
  0.75::factB.
  0.8::factC.
  %hop1
  0.2::factX:-and(factB,factC).
  0.0::factY:-and(factA,factC).
  0.2::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'Greg is a rhino' or 'Julius is white' or both.