It is probable that Gertrude is a cat. It is probably not the case that Bernhard is white. It is probable that Julius is a rhino. It is likely that if 'Bernhard is white and Julius is a rhino' then Sandra got the milk. There is little chance that if 'Bernhard is white' or 'Julius is a rhino' or both then Mary moved to the garden. It is highly likely that if 'Julius is a rhino and Gertrude is a cat' then Brian is a swan.
Chances are about even that 'Julius is a rhino and Brian is a swan'.
Chances are about even that 'Julius is a rhino and Brian is a swan'.
It is impossible that 'Julius is a rhino and Brian is a swan'.

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

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

  query(conclusion).
  
'Julius is a rhino and Brian is a swan'.