It is likely that Fred is in the office. Chances are about even that Brian is green. It is highly unlikely that Bernhard is a rhino. Chances are slight that if 'Brian is green' or 'Fred is in the office' or both then Lily is a rhino. It is probable that if 'Brian is green and Bernhard is a rhino' then Greg is yellow. It is impossible that if 'Brian is green and Bernhard is a rhino' then Sandra got the milk.
It is highly unlikely that 'Bernhard is a rhino' or 'Greg is yellow' or both.
It is highly unlikely that 'Bernhard is a rhino' or 'Greg is yellow' or both.
There is a better than even chance that 'Bernhard is a rhino' or 'Greg is yellow' 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.
  0.5::factB.
  0.05::factC.
  %hop1
  0.1::factX:-or(factB,factA).
  0.7::factY:-and(factB,factC).
  0.0::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Bernhard is a rhino' or 'Greg is yellow' or both.