In an effort to allow Primary Market Makers more flexibility in opening trading in a particular class of options, the International Securities Exchange, LLC (ISE) has filed a proposal with the Securities and Exchange Commission to replace references to the “primary market” for an underlying security in ISE Rule 701 with references to the “market for the underlying security.” ISE Rule 701(b)(2) currently requires Primary Market Makers to open each class of options promptly following the opening of the underlying security in the “primary market” where the underlying security is traded. The ISE believes that the term “primary market” has become increasingly difficult to define because underlying securities trade on multiple exchange platforms and other venues. Under the proposal, the term “market for the underlying security” would mean either the primary listing market, the primary volume market, or the first market to open the underlying security, as determined by the ISE on an issue-by-issue basis.  

http://www.ise.com/assets//documents//OptionsExchange//legal/proposed_rule_changes/2009/SR-ISE-2009-13$Proposed_Rule_Change_to_Revise_the_Definition_of_Primary_Market$20090318.pdf