reserve k,n for Element of NAT,
  a,Y for set,
  D,D1,D2 for non empty set,
  p,q for FinSequence of NAT;
reserve F,F1,G,G1,H,H1,H2 for CTL-formula;
reserve sq,sq9 for FinSequence;
reserve V for CTLModel;
reserve Kai for Function of atomic_WFF,the BasicAssign of V;
reserve f,f1,f2 for Function of CTL_WFF,the carrier of V;
reserve S for non empty set;
reserve R for total Relation of S,S;
reserve s,s0,s1 for Element of S;
reserve BASSIGN for non empty Subset of ModelSP(S);
reserve kai for Function of atomic_WFF,the BasicAssign of BASSModel(R,BASSIGN);

theorem Th17:
  for f,g being Assign of BASSModel(R,BASSIGN) holds s |= f 'or' g
  iff (s|= f or s|= g)
proof
  let f,g be Assign of BASSModel(R,BASSIGN);
  s |= f 'or' g iff not s|= 'not'(f) '&' 'not'(g) by Th12;
  then s |= f 'or' g iff not s|= 'not'(f) or not s|= 'not'(g) by Th13;
  hence thesis by Th12;
end;
