It is probably the case that Greg is a swan. We doubt that Brian is a lion. Chances are about even that John went to the kitchen. It is certain that if 'Brian is a lion' or 'John went to the kitchen' or both then Bernhard is a frog. It is likely that if 'Greg is a swan' or 'John went to the kitchen' or both then Julius is yellow. It is probably the case that if 'Greg is a swan' or 'John went to the kitchen' or both then Mary left the football.
It is almost certain that 'Julius is yellow and Greg is a swan'.
Chances are about even that 'Julius is yellow and Greg is a swan'.
It is almost certain that 'Julius is yellow 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
  0.7::factA.
  0.2::factB.
  0.5::factC.
  %hop1
  1.0::factX:-or(factB,factC).
  0.7::factY:-or(factA,factC).
  0.7::factZ:-or(factA,factC).

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

  query(conclusion).
  
'Julius is yellow and Greg is a swan'.