There is a very good chance that Bill went to the garden. We doubt that Gertrude is a sheep. There is a very good chance that Bernhard is a rhino. There is almost no chance that if 'Bill went to the garden' or 'Bernhard is a rhino' or both then Emily is a mouse. It is likely that if either 'Bill went to the garden' or 'Bernhard is a rhino' but not both then Brian is white. Chances are about even that if 'Bill went to the garden' or 'Gertrude is a sheep' or both then Lily is green.
It is impossible that 'Brian is white and Emily is a mouse'.
It is impossible that 'Brian is white and Emily is a mouse'.
There is a better than even chance that 'Brian is white and Emily is a mouse'.

  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
  0.8::factA.
  0.2::factB.
  0.8::factC.
  %hop1
  0.02::factX:-or(factA,factC).
  0.7::factY:-xor(factA,factC).
  0.5::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Brian is white and Emily is a mouse'.