There is a better than even chance that Greg is a rhino. It is certain that Gertrude is a mouse. It is unlikely that Sandra left the apple. We doubt that if 'Sandra left the apple and Greg is a rhino' then Mary went to the office. It is highly unlikely that if 'Sandra left the apple and Greg is a rhino' then Winona is a sheep. There is a very good chance that if either 'Sandra left the apple' or 'Gertrude is a mouse' but not both then Brian is a frog.
It is likely that 'Brian is a frog' or 'Mary went to the office' or both.
It is likely that 'Brian is a frog' or 'Mary went to the office' or both.
Chances are slight that 'Brian is a frog' or 'Mary went to the office' 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
  0.6::factA.
  1.0::factB.
  0.2::factC.
  %hop1
  0.2::factX:-and(factC,factA).
  0.05::factY:-and(factC,factA).
  0.8::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'Brian is a frog' or 'Mary went to the office' or both.