There is almost no chance that Brian is a lion. It is highly unlikely that Sumit is thirsty. There is little chance that Greg is a lion. It is probably not the case that if 'Greg is a lion and Sumit is thirsty' then Sandra left the football. It is highly likely that if either 'Greg is a lion' or 'Brian is a lion' but not both then Mary got the apple. There is almost no chance that if 'Sumit is thirsty and Brian is a lion' then John moved to the garden.
There is almost no chance that either 'John moved to the garden' or 'Brian is a lion' but not both.
There is almost no chance that either 'John moved to the garden' or 'Brian is a lion' but not both.
It is certain that either 'John moved to the garden' or 'Brian is a lion' but not both.

  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
  0.02::factA.
  0.05::factB.
  0.1::factC.
  %hop1
  0.25::factX:-and(factC,factB).
  0.9::factY:-xor(factC,factA).
  0.02::factZ:-and(factB,factA).

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

  query(conclusion).
  
Either 'John moved to the garden' or 'Brian is a lion' but not both.