We doubt that Jessica is a cat. Chances are about even that John dropped the milk. It is probable that Jeff went to the bedroom. It is highly likely that if 'Jessica is a cat and Jeff went to the bedroom' then Daniel got the football. It is improbable that if 'John dropped the milk' or 'Jessica is a cat' or both then Greg is a rhino. Chances are slight that if either 'John dropped the milk' or 'Jeff went to the bedroom' but not both then Bernhard is a swan.
Chances are about even that 'Bernhard is a swan and Greg is a rhino'.
It is impossible that 'Bernhard is a swan and Greg is a rhino'.
Chances are about even that 'Bernhard is a swan and Greg is a rhino'.

  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
  0.2::factA.
  0.5::factB.
  0.7::factC.
  %hop1
  0.9::factX:-and(factA,factC).
  0.1::factY:-or(factB,factA).
  0.1::factZ:-xor(factB,factC).

  %hop2
  conclusion:-and(factZ,factY).

  query(conclusion).
  
'Bernhard is a swan and Greg is a rhino'.