parametersin if equation

[Willi Braun]

Why is in the following model the variable b a structural parameter?
Or why is the user not allowed to change this parameter after translation?

loadString("
model A
  parameter Boolean b = true;
  Real x1,x2;
  Real y;
equation
  x1 = sin(time);
  x2 = cos(time);
  if b then
    y = x1^2+1;
  else
    y = x2^2-1;
  end if;
end A;
");
getErrorString();
instantiateModel(A);
getErrorString();

Result:

true
""
"class A
  parameter Boolean b = true;
  Real x1;
  Real x2;
  Real y;
equation
  x1 = sin(time);
  x2 = cos(time);
  y = 1.0 + x1 ^ 2.0;
end A;
"