Federal district court erred in construing patent for softball bat without supplying any information about accused infringing devices, since, without description of accused bats, reviewing court lacks full context of infringement action and claim construction component of infringement, and without that additional context, reviewing court cannot fully and confidently review infringement judgment, including its claim construction component; although accused product or process may not be used as form of extrinsic evidence to supply limitations for patent claim language, that rule of claim construction does not forbid awareness of accused product or process to supply parameters and scope of infringement analysis, including its claim construction component.