It is probably not the case that Fred went to the garden. Chances are about even that Mary left the football. It is likely that Bernhard is a swan. We doubt that if 'Fred went to the garden and Bernhard is a swan' then Gertrude is a mouse. There is a very good chance that if 'Bernhard is a swan' or 'Fred went to the garden' or both then Brian is a rhino. It is almost certain that if 'Fred went to the garden and Bernhard is a swan' then John got the milk.
There is a better than even chance that 'Gertrude is a mouse' or 'Brian is a rhino' or both.
There is a better than even chance that 'Gertrude is a mouse' or 'Brian is a rhino' or both.
It is impossible that 'Gertrude is a mouse' or 'Brian is a rhino' 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
  0.25::factA.
  0.5::factB.
  0.7::factC.
  %hop1
  0.2::factX:-and(factA,factC).
  0.8::factY:-or(factC,factA).
  0.95::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Gertrude is a mouse' or 'Brian is a rhino' or both.