as any system that:
(1) would constitute, maintain, or provide a marketplace or facilities for bringing together purchasers and sellers of securities or for otherwise performing with respect to securities the functions commonly performed by a stock
exchange under proposed Rule 3b-12 of the Exchange Act;64 and
(2) would not regulate its
members or surveil its own market.65 This proposed definition excludes trading systems that conduct a regulatory function because the Commission believes that self-regulatory systems should be registered as exchanges