It is certain that Bernhard is a rhino. It is certain that Gertrude is a mouse. It is highly likely that Yann is hungry. It is likely that if 'Gertrude is a mouse and Yann is hungry' then Julius is yellow. There is little chance that if 'Yann is hungry' or 'Bernhard is a rhino' or both then Mary got the apple. It is probably the case that if 'Yann is hungry' or 'Gertrude is a mouse' or both then John went to the bedroom.
It is unlikely that 'Bernhard is a rhino' or 'Yann is hungry' or both.
It is certain that 'Bernhard is a rhino' or 'Yann is hungry' or both.
It is unlikely that 'Bernhard is a rhino' or 'Yann is hungry' 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
  1.0::factA.
  1.0::factB.
  0.9::factC.
  %hop1
  0.7::factX:-and(factB,factC).
  0.1::factY:-or(factC,factA).
  0.7::factZ:-or(factC,factB).

  %hop2
  conclusion:-or(factA,factC).

  query(conclusion).
  
'Bernhard is a rhino' or 'Yann is hungry' or both.