Amazon.com Inc.'s fight to bar rival Barnesandnoble.com Inc. from using a patented single-click online purchasing method goes before a federal appeals court, which will hear arguments today in a case that could shape the future of Internet business. The U.S. Court of Appeals for the Federal Circuit in Washington will decide whether to lift a preliminary injunction blocking Barnesandnoble.com from using technology that enables online purchases with one click of a computer mouse. Amazon.com, the world's largest Internet retailer, claims exclusive rights to the technology. The case, which will be tried in Washington state, tests the limits of patents on basic Internet business methods. While companies such as Amazon.com seek to protect their innovations, critics say the patents are too freely granted and threaten to stifle the freewheeling Internet economy.