Chances are about even that Greg is a lion. It is impossible that Fred discarded the apple. It is highly unlikely that Jason is tired. There is almost no chance that if 'Fred discarded the apple and Greg is a lion' then Julius is a frog. It is probably the case that if either 'Greg is a lion' or 'Fred discarded the apple' but not both then John went to the office. It is improbable that if 'Jason is tired and Greg is a lion' then Sandra dropped the milk.
Chances are about even that 'Jason is tired' or 'John went to the office' or both.
Chances are about even that 'Jason is tired' or 'John went to the office' or both.
It is impossible that 'Jason is tired' or 'John went to the office' or both.

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

  %hop2
  conclusion:-or(factC,factY).

  query(conclusion).
  
'Jason is tired' or 'John went to the office' or both.