Nasdaq, the second-largest US equities market, is considering a series of joint ventures with some of the leading high-technology companies that trade on the exchange, in a plan that would culminate in a new Internet platform for trading its shares.

The plan is part of a larger proposal being designed to tighten Nasdaq's relationships with the broker-dealers that handle trading and its many high-tech companies that list shares on the exchange. Talks with some of these companies, including Microsoft, are believed to be under way.