There is a very good chance that Gertrude is a mouse. There is a better than even chance that Greg is gray. It is probably the case that Jeff left the apple. It is likely that if 'Jeff left the apple and Gertrude is a mouse' then Julius is a swan. It is likely that if 'Greg is gray' or 'Jeff left the apple' or both then John discarded the milk. There is little chance that if 'Greg is gray' or 'Gertrude is a mouse' or both then Bernhard is a rhino.
It is certain that 'Greg is gray and Gertrude is a mouse'.
Chances are about even that 'Greg is gray and Gertrude is a mouse'.
It is certain that 'Greg is gray and Gertrude is a mouse'.

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

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

  query(conclusion).
  
'Greg is gray and Gertrude is a mouse'.