There is a very good chance that Greg is gray. It is almost certain that Brian is a rhino. There is a better than even chance that Gertrude is a mouse. There is little chance that if 'Gertrude is a mouse and Brian is a rhino' then John moved to the office. It is almost certain that if 'Brian is a rhino and Gertrude is a mouse' then Mary went to the garden. It is almost certain that if 'Brian is a rhino' or 'Gertrude is a mouse' or both then Bernhard is a frog.
We believe that 'Greg is gray and Bernhard is a frog'.
We believe that 'Greg is gray and Bernhard is a frog'.
It is improbable that 'Greg is gray and Bernhard is a frog'.

  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
  0.8::factA.
  0.95::factB.
  0.6::factC.
  %hop1
  0.1::factX:-and(factC,factB).
  0.95::factY:-and(factB,factC).
  0.95::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Greg is gray and Bernhard is a frog'.