It is unlikely that Greg is a rhino. It is highly likely that Brian is a swan. We believe that John went to the garden. We doubt that if 'John went to the garden and Brian is a swan' then Sandra left the milk. It is highly likely that if either 'Greg is a rhino' or 'John went to the garden' but not both then Lily is yellow. It is likely that if 'Greg is a rhino' or 'John went to the garden' or both then Jeff dropped the apple.
We doubt that 'Greg is a rhino and Brian is a swan'.
We doubt that 'Greg is a rhino and Brian is a swan'.
It is likely that 'Greg 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
  0.2::factA.
  0.9::factB.
  0.75::factC.
  %hop1
  0.2::factX:-and(factC,factB).
  0.9::factY:-xor(factA,factC).
  0.7::factZ:-or(factA,factC).

  %hop2
  conclusion:-and(factA,factB).

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