notionalStepSchedule & notionalStepParameters

[brusckeabax]

These two elements of the type Notional seem to rule-out the possibility of an amortizing notional schedule. The element notionalStepSchedule of type NonNegativeAmountSchedule is required in the type Notional. I take it that “NonNegative…” supports accretion but rules-out amortization. Why should amortization be ruled out? The element notionalStepParameters of type NotionalStepRule is optional in the type Notional. Notional’s documentation reads: “An type … The notional schedule will be captured explicitly, … A parametric representation of the rules defining the notional step schedule can optionally be included.” I read this definition to mean that the author mandates that the Notional be defined as a NonNegativeAmountSchedule; and, that a user may – optionally – explain how that N-N-AmountSchedule was constructed by includng a NotionalStepRule. I.e., a NotionalStepRule is complementary, but not an alternative to the N-N-AmountSchedule. The definition of NotionalStepRule reads: “A type … This parametric representation is intended to cover the more common amortizing/accreting.” Here, the author of NotionalStepRule contemplates “amortizing” which seems to be incompatable with the mandatory notionalStepSchedule of type NonNegativeAmountSchedule. Therefore, while NotionalStepRule would support an amortizing Notional, it would be incompatable with notionalStepSchedule of type NonNegativeAmountSchedule. Since the latter is mandatory while the former is optional, a user cannot create an amortizing NotionalStepRule without violating the constraints of NonNegativeAmountSchedule. It seems to me that either: – notionalStepSchedule should not be of type NonNegativeAmountSchedule; or, notionalStepSchedule should be optional so that NotionalStepRule could provide a parametric representation of an amortizing notional schedule. Either of these preceptions implies an error in FpML; and so, I presume I’m misintrepreting the prohibition of amortizing notional schedules. Can anyone explain the error of my interpretation? Thanks Mark

[brusckeabax]

I think I’ve found my answer. I see that the type NonNegativeStep is defined as: “The non-negative rate or amount which becomes effective on the associated stepDate.” I had taken “step” to represent the value of the delta from the previous value. So, if an initial value of 100 declined by 10% per step we would see: -10 -10 -10 … It’s now clear to me that each step represents the value on the corresponding date. So, my example should appear: 90 80 70 … Moreover, it’s now clear why it should be non-negative. The swap should not have negative notionals. (Nor is a negative intrest rate contemplated were a steped schedule represent a series of stepped coupons.)

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