WILL_NOT_BE_THE_SAME

From ASCEND

WILL_NOT_BE_THE_SAME is used in the declarations of parametric models to enforce that parameters or parts of the parameters won't have already been merged using ARE_THE_SAME. This is useful in ensuring model reusability, because in many case, merging parameters will result in wrong results calculated by a model.

This statement is very unlikely to be needed in your first few models.

From the user's manual:

Structural condition statement restricting objects in a forward declaration. We apologize for the length of this key word, but we bet it is easy to remember. The objects passed to a parameterized type definition can be constrained to have arbitrary parts be distinct instances before the parameterized object is constructed. At present the constraint is only enforced when the objects are being passed.

See also WILL_BE_THE_SAME..