There is a better than even chance that Jessica is a cat. Chances are about even that Gertrude is a wolf. Chances are about even that Fred discarded the apple. There is little chance that if 'Gertrude is a wolf and Jessica is a cat' then Bernhard is green. It is unlikely that if 'Fred discarded the apple and Gertrude is a wolf' then Brian is gray. It is likely that if 'Gertrude is a wolf and Jessica is a cat' then John moved to the office.
We believe that 'Gertrude is a wolf' or 'Fred discarded the apple' or both.
We believe that 'Gertrude is a wolf' or 'Fred discarded the apple' or both.
There is little chance that 'Gertrude is a wolf' or 'Fred discarded the apple' 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.
  0.5::factB.
  0.5::factC.
  %hop1
  0.1::factX:-and(factB,factA).
  0.2::factY:-and(factC,factB).
  0.7::factZ:-and(factB,factA).

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

  query(conclusion).
  
'Gertrude is a wolf' or 'Fred discarded the apple' or both.