It is likely that Brian is white. Chances are slight that John moved to the garden. It is probable that Bernhard is a frog. There is little chance that if 'Brian is white and Bernhard is a frog' then Greg is a rhino. It is probably not the case that if 'Brian is white and John moved to the garden' then Sandra dropped the milk. It is probably not the case that if 'John moved to the garden' or 'Bernhard is a frog' or both then Mary got the football.
We believe that 'Mary got the football and Brian is white'.
There is little chance that 'Mary got the football and Brian is white'.
We believe that 'Mary got the football and Brian is white'.

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

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

  query(conclusion).
  
'Mary got the football and Brian is white'.