Mountain View, Calif.-Ariba Inc. Monday acquired collaborative supply chain vendor Agile Software Corp., placing a $2.55 billion stock-for-stock bet that Agile has the technology it needs to move beyond procurement into full-fledged b-to-b collaboration. Industry watchers have been waiting for Ariba to acquire supply chain technology, in part because its partnership with i2 Technologies Inc. has seemed to be coming apart at the seams for months. Ariba today is best known for its e-procurement and e-marketplace platforms, but the industry is quickly moving toward private marketplaces where companies not only buy and sell but also handle all their supply chain collaboration online. Agile's tools help companies manage their manufacturing processes, including b-to-b product design, sourcing, procurement, manufacturing and sales. The two companies said they'll begin integrating their products and commerce services networks immediately, with a road map to be laid out later this quarter.