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Vol_Spec__Vol_Type

Vol Type refers to List of definitions of what "volatility" exactly (mathematically) means in the context of a given stochastic process, a given risk factor and some fixed future time.
Available Vol Type types:
Black
Appropriate when the value x(T) of the Quotable in
Key Vol Spec::Ref Quotable at a given time T with respect to the given risk factor is distributed in any fashion.
Then the Black volatility is defined as the function σ(K) defined by requiring that the equality E{ max(x(T)-K,0) } = Black(K,σ) holds for all real values K.
Here E denotes the Expectation operator with respect to a measure where x behaves as martingale and Black(K,σ) is defined to equal E{ max(y(T)-K,0) } for some y diffused as dy = σydw
In the trivial case where all strikes K map to the same flat value σ, the value at time T is the single number σ.
SABR
Appropriate when the value x(T) of the Quotable in
Key Vol Spec::Ref Quotable at a given time T with respect to the given risk factor derives from the following SDE:
dx = α(x^β)dw
wherew is a Wiener process, β is constant and α is the forward's stochastic volatility, which itself follows the SDE:
dα = ναdω
where v is constant and ω is another Wiener process having correlation ρ with w. Web reference available
here
Due to the absence of a drift term, x represents the value of some forward, such as a forward rate or a forward stock price.