It is probable that Sandra got the football. It is impossible that John grabbed the apple. It is improbable that Greg is a swan. It is impossible that if 'Greg is a swan and John grabbed the apple' then Gertrude is a sheep. It is highly unlikely that if 'John grabbed the apple and Sandra got the football' then Bernhard is a rhino. It is likely that if either 'Greg is a swan' or 'John grabbed the apple' but not both then Brian is yellow.
We believe that 'Sandra got the football and Greg is a swan'.
It is highly unlikely that 'Sandra got the football and Greg is a swan'.
We believe that 'Sandra got the football and Greg 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.
  0.0::factB.
  0.1::factC.
  %hop1
  0.0::factX:-and(factC,factB).
  0.05::factY:-and(factB,factA).
  0.7::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'Sandra got the football and Greg is a swan'.