There is a better than even chance that Greg is a swan. It is probably the case that John dropped the milk. It is highly likely that Bill went to the kitchen. There is a very good chance that if 'Greg is a swan and John dropped the milk' then Gertrude is a cat. It is almost certain that if either 'John dropped the milk' or 'Bill went to the kitchen' but not both then Brian is a rhino. It is likely that if either 'Greg is a swan' or 'John dropped the milk' but not both then Bernhard is white.
It is almost certain that 'Bill went to the kitchen and Greg is a swan'.
Chances are about even that 'Bill went to the kitchen and Greg is a swan'.
It is almost certain that 'Bill went to the kitchen and Greg is a swan'.

  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
  0.6::factA.
  0.7::factB.
  0.9::factC.
  %hop1
  0.8::factX:-and(factA,factB).
  0.95::factY:-xor(factB,factC).
  0.7::factZ:-xor(factA,factB).

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

  query(conclusion).
  
'Bill went to the kitchen and Greg is a swan'.