Аннотация:infringement even when the accused product does not literally satisfy each element of the patent, if there is substantial equivalence as to each element.The test of equivalence is the known interchangeability of claimed and accused elements at the time of (alleged) infringement.A number of factors unique to software and the software industry-a culture of reuse and incremental improvement, a lack of reliance on systems of formal documentation used in other fields, the short effective life of software innovations, and the inherent plasticity of code-severely complicate post hoc assessments of the "known interchangeability" of software elements.A standard for equivalence of code elements that ignores these factors risks stifling legitimate, successful efforts to design around existing software patents.To avoid this danger, courts should construe software claims narrowly, and should refuse a finding of equivalence if the accused element is "interchangeable" with prior art that should have narrowed the original patent, or if the accused improvement is too many generations removed from the original invention.
