Detroit--Toyota Motor North America said late Wednesday that it will form an electronic marketplace on the Internet, aimed at streamlining the $100 billion automotive replacement parts market in the U.S. Toyota signed a definitive agreement to work with i2 Technologies, Irving, Texas, to develop and operate the site, which will be named iStarXchange. The two companies said they anticipate the site will begin operation by July. Toyota said the automotive replacement parts market consists of 160,000 buyers, 66,000 sellers and a catalog with millions of different part numbers--dynamics that make it ripe for Internet development. Toyota and i2 will jointly own the venture, which will operate as an independent start-up. The move underscores i2's transition from a vendor of software for automating supply chains to a Web site specialist.