Affirmative Obligation
An obligation of NYSE specialists to enter the market on a particular security (either by posting or bidding and ask) when there is not sufficient market demand and supply to efficiently match orders.
Investopedia Commentary
The affirmative obligation requires specialists to create a market for a security when public demand or supply is ineffective and can not create it for itself.
See also: Negative Obligation, NYSE, Principal, Specialist, Trading Ahead