Rushing to build a complete b-to-b trading exchange for direct materials purchasing, Ariba Inc., Mountian View, Calif., said Tuesday that it has formed a strategic alliance with Descartes Systems Group Inc., Waterloo, Ontario, to build Internet services for fulfillment of an order. The deal means Ariba, Mountain View, Calif., will work with Descartes, which specializes in providing e-commerce links for shipping companies. Fulfillment is considered a critical step in building e-commerce platforms that serve factories. That's because middleman distributors, positioned on the factory floor, have typically managed the fulfillment of goods. E-commerce evangelists argue that a closed-loop Internet system that includes fulfillment can eventually replace those distributors by allowing factory employees to pick the right parts. Established distributors say it'll be close to impossible to create a self-service application that replaces the expertise and customer service they deliver along with their products.