It is certain that Greg is yellow. There is little chance that Jessica is a sheep. There is a very good chance that John took the football. It is improbable that if either 'Jessica is a sheep' or 'John took the football' but not both then Bernhard is a rhino. It is probably not the case that if either 'John took the football' or 'Jessica is a sheep' but not both then Brian is a frog. It is probably the case that if 'John took the football and Greg is yellow' then Julius is a swan.
It is certain that 'Brian is a frog and Jessica is a sheep'.
It is impossible that 'Brian is a frog and Jessica is a sheep'.
It is certain that 'Brian is a frog and Jessica is a sheep'.

  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
  1.0::factA.
  0.1::factB.
  0.8::factC.
  %hop1
  0.1::factX:-xor(factB,factC).
  0.25::factY:-xor(factC,factB).
  0.7::factZ:-and(factC,factA).

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

  query(conclusion).
  
'Brian is a frog and Jessica is a sheep'.