Boston--Advanstar, which publishes Travel Agent and produces the MAGIC International trade show, announced Wednesday that it has formed a strategic alliance with PurchasePro.com, an electronic-commerce service provider, to create 20 business-to-business vertical communities on the Internet. Using a strategy similar to Horsham, Pa.-based VerticalNet, Advanstar and PurchasePro.com will build vertical Web portals that allow businesspeople to gather information, research, source, bid, buy and sell electronically. Additionally, these Web sites will offer industry news, job listings, chat rooms and auctions. The sites will be designed to mesh with the market ``clusters'' Advanstar already serves with its magazines, directories, trade shows and conferences. With the agreement, Advanstar, which is owned by Hellman & Friedman Capital Partners III, will acquire an equity stake in PurchasePro.com, which will receive more than $5 million to create the vertical Web sites and hosting fees of about $1.6 million per year. Advanstar and PurchasePro.com will share transactional and advertising revenue created by the sites.