There is a very good chance that Greg is a swan. It is unlikely that John discarded the apple. It is probably the case that Mary got the football. Chances are slight that if 'John discarded the apple and Greg is a swan' then Sandra left the milk. It is almost certain that if 'Mary got the football and John discarded the apple' then Jeff went to the bedroom. It is probably the case that if either 'John discarded the apple' or 'Greg is a swan' but not both then Yann is tired.
There is little chance that 'Mary got the football and John discarded the apple'.
There is little chance that 'Mary got the football and John discarded the apple'.
It is likely that 'Mary got the football and John discarded the apple'.

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

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

  query(conclusion).
  
'Mary got the football and John discarded the apple'.