It is probable that Mary went to the office. There is a better than even chance that Julius is yellow. We doubt that John is in the garden. It is improbable that if either 'Mary went to the office' or 'John is in the garden' but not both then Gertrude is a sheep. It is probably not the case that if 'Mary went to the office and John is in the garden' then Daniel grabbed the milk. We doubt that if 'John is in the garden' or 'Mary went to the office' or both then Greg is a lion.
There is almost no chance that 'John is in the garden' or 'Mary went to the office' or both.
We believe that 'John is in the garden' or 'Mary went to the office' or both.
There is almost no chance that 'John is in the garden' or 'Mary went to the office' or 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.
  0.6::factB.
  0.2::factC.
  %hop1
  0.1::factX:-xor(factA,factC).
  0.25::factY:-and(factA,factC).
  0.2::factZ:-or(factC,factA).

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

  query(conclusion).
  
'John is in the garden' or 'Mary went to the office' or both.