 In 1996, AT&T filed a patent infringement suit against Excel, including some specific method or process claims related to the step of "generating a message record for an interexchange call between an originating subscriber and a terminating subscriber," and the use of primary interexchange carrier (PIC) indicator in the message record.On March 27, 1998, the District Court of Delaware concluded
 that the invention was not patentable subject matter because the claims implicitly recite a mathematical algorithm.The trial court, on summary judgment, held all of the method claims at issue invalid for failure to qualify as statutory subject matter.