It is highly likely that Brian is a rhino. It is probable that Mary took the football. We doubt that Bernhard is yellow. It is probable that if either 'Bernhard is yellow' or 'Brian is a rhino' but not both then Greg is a lion. It is highly unlikely that if 'Bernhard is yellow' or 'Brian is a rhino' or both then Gertrude is a sheep. There is little chance that if 'Mary took the football' or 'Brian is a rhino' or both then John went to the bedroom.
It is probably not the case that 'Bernhard is yellow' or 'Brian is a rhino' or both.
It is highly likely that 'Bernhard is yellow' or 'Brian is a rhino' or both.
It is probably not the case that 'Bernhard is yellow' or 'Brian is a rhino' 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.
  0.7::factB.
  0.2::factC.
  %hop1
  0.7::factX:-xor(factC,factA).
  0.05::factY:-or(factC,factA).
  0.1::factZ:-or(factB,factA).

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

  query(conclusion).
  
'Bernhard is yellow' or 'Brian is a rhino' or both.