There is little chance that Winona is a sheep. There is almost no chance that Brian is a frog. We believe that Fred went to the garden. It is highly likely that if 'Brian is a frog' or 'Fred went to the garden' or both then Mary dropped the apple. It is unlikely that if 'Brian is a frog' or 'Fred went to the garden' or both then Gertrude is a wolf. It is probably not the case that if either 'Brian is a frog' or 'Fred went to the garden' but not both then Greg is a lion.
There is a very good chance that 'Brian is a frog and Mary dropped the apple'.
There is almost no chance that 'Brian is a frog and Mary dropped the apple'.
There is a very good chance that 'Brian is a frog and Mary dropped the apple'.

  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
  0.1::factA.
  0.02::factB.
  0.75::factC.
  %hop1
  0.9::factX:-or(factB,factC).
  0.2::factY:-or(factB,factC).
  0.25::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Brian is a frog and Mary dropped the apple'.