Whether the doctrine of equivalents is applicable for the product at issue may be determined by function-way-result triple-identity test. However, due to the advance of science and technology, the complexity of products or processes has increased. Therefore, sometimes way, function and result comparison is not sufficient to determine whether substantive differences exist between the product at issue and the patent at issue. Therefore, there are other theories to help determining the substantive differences between the patent and the allegedly infringing product or process, such as the insubstantial test and the interchangeability test. In other words, the triple-identity test is not the only way for examining equivalence. The equivalent range that extent the range of a patent claim for a person having ordinary skill in the art should be decided in each case. That is, to determine whether it is obvious for a person having ordinary skill in the art by comparing the function and result of the product at issue to the technical characteristics of the patent at issue

Doctrine of Equivalents、Triple-identity test、Substantial Difference、Test Possibility、Interchangeability