The parties may agree to replace an existing obligation with a new one that has a different subject or legal basis (e.g., the contracting parties of a sales agreement for the purchase of a construction machine replace it with a gift agreement for the same machine).¹⁹² Novation is not presumed; therefore, if the parties did not explicitly express their intent for the existing obligation to cease when creating the new one, the previous obligation does not terminate but continues to exist alongside the new one.¹⁹³