There is a better than even chance that Brian is a rhino. It is highly likely that Julius is a swan. It is probably not the case that John discarded the apple. It is unlikely that if either 'Julius is a swan' or 'Brian is a rhino' but not both then Greg is yellow. It is impossible that if 'John discarded the apple and Brian is a rhino' then Jeff went to the bedroom. We believe that if 'Julius is a swan' or 'Brian is a rhino' or both then Bernhard is a frog.
It is certain that 'Brian is a rhino and Greg is yellow'.
There is almost no chance that 'Brian is a rhino and Greg is yellow'.
It is certain that 'Brian is a rhino and Greg is yellow'.

  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
  0.6::factA.
  0.9::factB.
  0.25::factC.
  %hop1
  0.2::factX:-xor(factB,factA).
  0.0::factY:-and(factC,factA).
  0.75::factZ:-or(factB,factA).

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

  query(conclusion).
  
'Brian is a rhino and Greg is yellow'.