We doubt that John went to the hallway. Chances are about even that Gertrude is a sheep. It is almost certain that Mary left the football. It is likely that if 'John went to the hallway and Mary left the football' then Sandra dropped the milk. Chances are slight that if 'Gertrude is a sheep and John went to the hallway' then Emily is a mouse. There is almost no chance that if either 'Gertrude is a sheep' or 'John went to the hallway' but not both then Bernhard is a rhino.
Chances are about even that 'Gertrude is a sheep and Mary left the football'.
Chances are about even that 'Gertrude is a sheep and Mary left the football'.
It is impossible that 'Gertrude is a sheep and Mary left the football'.

  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
  0.2::factA.
  0.5::factB.
  0.95::factC.
  %hop1
  0.7::factX:-and(factA,factC).
  0.1::factY:-and(factB,factA).
  0.02::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Gertrude is a sheep and Mary left the football'.