It is almost certain that Brian is a frog. Chances are about even that Bill left the milk. It is impossible that Greg is yellow. It is likely that if 'Greg is yellow' or 'Brian is a frog' or both then Gertrude is a mouse. There is little chance that if 'Bill left the milk' or 'Greg is yellow' or both then Mary got the football. It is probably the case that if either 'Greg is yellow' or 'Bill left the milk' but not both then Bernhard is a swan.
It is almost certain that 'Bill left the milk' or 'Bernhard is a swan' or both.
Chances are about even that 'Bill left the milk' or 'Bernhard is a swan' or both.
It is almost certain that 'Bill left the milk' or 'Bernhard is a swan' 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
  0.95::factA.
  0.5::factB.
  0.0::factC.
  %hop1
  0.7::factX:-or(factC,factA).
  0.1::factY:-or(factB,factC).
  0.7::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'Bill left the milk' or 'Bernhard is a swan' or both.