It is highly unlikely that Gertrude is a sheep. It is highly unlikely that Jessica is a mouse. There is a very good chance that Mary went to the kitchen. It is probable that if 'Mary went to the kitchen and Gertrude is a sheep' then Brian is a swan. It is probably not the case that if either 'Gertrude is a sheep' or 'Mary went to the kitchen' but not both then John put down the apple. It is unlikely that if 'Gertrude is a sheep and Mary went to the kitchen' then Bernhard is yellow.
There is a very good chance that 'Jessica is a mouse and Brian is a swan'.
It is impossible that 'Jessica is a mouse and Brian is a swan'.
There is a very good chance that 'Jessica is a mouse and Brian 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
  0.05::factA.
  0.05::factB.
  0.8::factC.
  %hop1
  0.7::factX:-and(factC,factA).
  0.25::factY:-xor(factA,factC).
  0.2::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Jessica is a mouse and Brian is a swan'.