It is highly likely that Brian is a lion. It is almost certain that Gertrude is a mouse. It is likely that Greg is gray. We doubt that if 'Gertrude is a mouse and Greg is gray' then Fred moved to the office. It is likely that if 'Brian is a lion' or 'Gertrude is a mouse' or both then John went to the garden. It is unlikely that if 'Greg is gray' or 'Brian is a lion' or both then Mary took the football.
There is a very good chance that 'Gertrude is a mouse and Fred moved to the office'.
There is little chance that 'Gertrude is a mouse and Fred moved to the office'.
There is a very good chance that 'Gertrude is a mouse and Fred moved to the office'.

  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
  0.9::factA.
  0.95::factB.
  0.7::factC.
  %hop1
  0.2::factX:-and(factB,factC).
  0.7::factY:-or(factA,factB).
  0.2::factZ:-or(factC,factA).

  %hop2
  conclusion:-and(factB,factX).

  query(conclusion).
  
'Gertrude is a mouse and Fred moved to the office'.