It is probably the case that Emily is a mouse. There is a very good chance that Bill left the football. Chances are slight that Brian is gray. It is unlikely that if 'Brian is gray and Bill left the football' then Bernhard is a rhino. It is highly unlikely that if 'Brian is gray and Emily is a mouse' then Greg is a lion. There is a very good chance that if 'Bill left the football' or 'Brian is gray' or both then John took the apple.
It is probable that 'Brian is gray' or 'Bernhard is a rhino' or both.
Chances are slight that 'Brian is gray' or 'Bernhard is a rhino' or both.
It is probable that 'Brian is gray' or 'Bernhard is a rhino' 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
  0.7::factA.
  0.8::factB.
  0.1::factC.
  %hop1
  0.2::factX:-and(factC,factB).
  0.05::factY:-and(factC,factA).
  0.8::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Brian is gray' or 'Bernhard is a rhino' or both.