It is highly unlikely that Winona is a mouse. There is a very good chance that Mary went to the office. Chances are slight that Brian is a lion. It is improbable that if either 'Winona is a mouse' or 'Brian is a lion' but not both then John left the football. Chances are about even that if 'Brian is a lion and Mary went to the office' then Gertrude is a mouse. It is probably the case that if 'Winona is a mouse and Mary went to the office' then Julius is a lion.
There is a better than even chance that 'John left the football' or 'Brian is a lion' or both.
Chances are slight that 'John left the football' or 'Brian is a lion' or both.
There is a better than even chance that 'John left the football' or 'Brian is a lion' 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
  0.05::factA.
  0.8::factB.
  0.1::factC.
  %hop1
  0.1::factX:-xor(factA,factC).
  0.5::factY:-and(factC,factB).
  0.7::factZ:-and(factA,factB).

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

  query(conclusion).
  
'John left the football' or 'Brian is a lion' or both.