It is probable that John went to the garden. There is a very good chance that Emily is a mouse. It is certain that Bernhard is green. We doubt that if either 'John went to the garden' or 'Bernhard is green' but not both then Daniel got the football. There is little chance that if 'John went to the garden and Bernhard is green' then Greg is yellow. There is almost no chance that if 'Bernhard is green' or 'John went to the garden' or both then Mary is in the school.
There is almost no chance that either 'Greg is yellow' or 'Emily is a mouse' but not both.
We believe that either 'Greg is yellow' or 'Emily is a mouse' but not both.
There is almost no chance that either 'Greg is yellow' or 'Emily is a mouse' 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
  0.7::factA.
  0.8::factB.
  1.0::factC.
  %hop1
  0.2::factX:-xor(factA,factC).
  0.1::factY:-and(factA,factC).
  0.02::factZ:-or(factC,factA).

  %hop2
  conclusion:-xor(factY,factB).

  query(conclusion).
  
Either 'Greg is yellow' or 'Emily is a mouse' but not both.