We believe that Mary went to the hallway. It is likely that Greg is a rhino. We doubt that Jessica is a cat. There is a very good chance that if 'Greg is a rhino and Mary went to the hallway' then Sandra left the milk. There is little chance that if 'Mary went to the hallway' or 'Jessica is a cat' or both then Bernhard is a lion. There is little chance that if either 'Mary went to the hallway' or 'Jessica is a cat' but not both then John moved to the office.
It is probable that 'John moved to the office' or 'Greg is a rhino' or both.
It is probable that 'John moved to the office' or 'Greg is a rhino' or both.
There is almost no chance that 'John moved to the office' or 'Greg is a rhino' 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
  0.75::factA.
  0.7::factB.
  0.2::factC.
  %hop1
  0.8::factX:-and(factB,factA).
  0.1::factY:-or(factA,factC).
  0.1::factZ:-xor(factA,factC).

  %hop2
  conclusion:-or(factZ,factB).

  query(conclusion).
  
'John moved to the office' or 'Greg is a rhino' or both.