Patent infringement analysis involves a complex series of steps. When the technical features of the disputed infringing product are deemed not to read on the claims of the disputed patent, the doctrine of equivalents (DOE) is generally applied. Under the DOE, the comparison can be carried out either "element by element" (i.e., individually comparing each element of the disputed infringing product to the disputed patent claims to determine whether such element has the same function, method, and result as the disputed patent claims) or "as a whole" (i.e., comparing the entire scope of the disputed infringing product with the disputed patent claims to determine whether the disputed infringing product has the same function, method, and result as the disputed patent claims). However, there currently seems to be no consensus on which method should be applied in practice.

 

The Intellectual Property Office (referred to as the IPO) of the Ministry of Economic Affairs, in its "Guidelines for Infringement Verification (Draft)" released in 2004, was the first to state in section 5, (4) "Points to Note on Applying the Doctrine of Equivalents": "...the comparison based on the doctrine of equivalents should be conducted by an 'element by element' comparison of the technical features of the claimed invention after interpretation to the corresponding elements, components, steps, or their combinations of the subject being considered, in order to determine whether there is any non-literal equivalence. The comparison should not be based on the 'as a whole' comparison of the entire claims of the claimed invention to the subject being considered...", which indicates that the "element by element" principle should be applied.

 

Accordingly, the Intellectual Property and Commercial Court (referred to as the IPCC) initially applied the "element by element" principle in practice. For instance, in the Ming Zhuan Su Zi Decision No. 64 of 2008 and the Ming Zhuan Su Zi Decision No. 38 of 2009 issued by IPCC, the IPCC stated: "...regarding the application of the doctrine of equivalents, under the 'all-elements rule,' the 'element by element' comparison principle should be applied. Each technical feature should be compared individually to determine whether the technical means, function, and result of each technical feature are substantially the same as those of the claimed invention, rather than conducting a comparison based on the claims as a whole..." However, in the Tai Shang Zi Decision No. 406 dated March 11, 2010, the Supreme Court stated: "...the determination of whether the doctrine of equivalents applies is not limited to the number of technical features of the subject being considered that correspond individually to the claims when interpreting the 'all-elements rule.' Instead, it should be determined whether the technical features of the subject being considered correspond to the claims based on the functions of the technical features. The decision of the United States Court of Appeals for the Federal Circuit in 1989 concerning a patent infringement lawsuit regarding an optical fiber signal waveguide as an example, it explained that, according to the 'all-elements rule,' it is necessary to find every technical feature or equivalent technical content of the claimed invention in the subject matter in question, but there does not need to be a one-to-one correspondence. It suggested that an overall comparison should be made to see if the two are substantially the same...", which seems to acknowledge the adoption of the "as a whole" principle for comparisons made under the doctrine of equivalents, rather than the "element by element" principle. 

 

Subsequently, in the Tai Shang Zi Decision No. 230 dated February 16, 2012, the Supreme Court adopted the same position, and the original decision Ming Zhuan Shang Geng Yi Zi Decision No. 12 of 2010 rendered by the IPCC was annulled and remanded. In the original decision, the IPCC used the "element by element" principle to determine that the defendant's product did not constitute infringement. After such decision was annulled and remanded by the Supreme Court, the IPCC rendered the Ming Zhuan Shang Geng Er Zi Decision No. 2 of 2012, stating: "...as for the argument made by the appellant that the technical features of the claimed invention and the corresponding elements of the disputed infringing product should be compared individually, it should be noted that the doctrine of equivalents is intended to prevent a third party from making non-substantial changes to the technical features of the claimed invention in order to evade infringement liability. Since most of the technical features of the claimed invention are present in the disputed product, with the only difference being the different placement of 'inflatable pumps, venting valves, and buzzers,' while the functions of inflation and deflation as well as the sound warning effect generated by the different positions, as well as the effects of pneumatic massage and sound warning, are the same as those of the claimed invention, it is difficult to conclude that the disputed product is not subject to the doctrine of equivalents..." It is evident that the comparison under the doctrine of equivalents has essentially shifted to the "as a whole" principle, and the defendant's product was found to constitute equivalent infringement.

 

However, despite these developments, subsequent interpretations by the IPO and other decisions by the IPCC seem not to have made the "as a whole" principle the basis for judging or trying cases involving equivalent infringement. Instead, the "element by element" principle is still commonly seen as the standard. Specifically, in the "Guidelines for Infringement Verification" issued by the IPO in 2016, section 4.2.1 "Principle of Judgment on the Doctrine of Equivalents" states: "...when judging whether the claims of the disputed patent and the accused infringing object are equivalent, the 'as a whole' comparison should not be used. That is, the comparison should not be directly based on the overall technical means of the claims of the disputed patent and the overall technical content of the accused infringing object. Instead, the 'element by element' comparison should be used, that is, the technical features of the claims of the disputed patent and the parts of the technical content of the accused infringing object that are not the same should be compared individually to determine whether such corresponding technical features are equivalent..." This indicates that the "element by element" principle is still applicable. Moreover, in the Ming Zhuan Su Zi Decision No. 104 of 2017, the IPCC not only expressly adopted the "element by element" principle but also indicated the rejection of the application of the "as a whole" principle: "...since the determination of equivalent infringement is premised on the fact that the accused infringing product does not fall within the defined scope of the claims of the patent, for the sake of maintaining the predictability and clarity of the scope of the patent right, the technical features of the accused infringing product must be clearly and substantially the same as the technical features not covered by the literal scope of the claims. The 'as a whole' comparison of the claims of the patent and the accused infringing product, or a simple determination of substantial sameness based on the same purpose or effect, cannot be used to ambiguously conclude that the two are substantially the same..." Similarly, in the Ming Zhuan Su Zi Decision No. 19 of 2022, which was rendered on June 12, 2023, the IPCC emphasized once again that the principle of equivalence should be determined using the "element by element" principle, and explicitly stated its position of rejecting the application of the "as a whole" principle: "...the doctrine of equivalents is based on the principles of protecting the interests of the patentee and preventing others from making non-substantial changes to the technical features of the disputed patent claims and thereby evading infringement liability. Regarding the principle of judgment based on the doctrine of equivalents, the 'as a whole' comparison of the claims of the disputed patent and the accused infringing object should not be used. Instead, the 'element by element' comparison should be used. That is, the technical features of the claims of the disputed patent and the technical content of the accused infringing object that are not the same should be compared individually to determine whether such corresponding technical features are equivalent..."

 

Therefore, although both the "element by element" and the "as a whole" comparisons have their supporting stances based on legal principles and practices in various countries, from a technical perspective, the comparison principle to be applied in a particular case may need to be determined based on the circumstances of such case, and cannot be definitively generalized. To illustrate, consider two situations: Situation One: The claimed invention includes A and B, and A includes X, while the accused product includes A' and B', and B' includes X' Situation Two: The claimed invention includes a, b, and nails, while the accused product includes a', b', and screws. When these two situations are subject to a comparison under the doctrine of equivalents, it may be argued that either the "as a whole" principle or the "element by element" principle should be adopted, depending on which best serves the interests of the parties and fulfills the purpose of patent protection. Parties involved in litigation should carefully consider and evaluate this aspect while forming their litigation strategies, and the courts should take an all-encompassing view in making decisions.