The purpose of the patent system is to encourage applicants to publicly disclose the result of their research and development by granting them exclusive rights, so that the public can use such published inventions or creations.  For this reason, there is no need to grant a patent for an invention or creation that has been known to the public before the patent was filed. This is the legal requirement for the patentability of "novelty" as stipulated in paragraph 1, Article 22 of the Taiwan Patent Act.

According to the current Patent Examination Guidelines, there are three ways to determine novelty: Determining whether the invention claimed in a patent application is "exactly equivalent" to the prior art disclosed in the citation document; or "whether the only difference between both is the form of text description or whether the technical features can be directly and unambiguously perceived in the citation document;" or "the only difference between both is that the corresponding technical features are superordinate and subordinate concepts".  As long as the claimed invention or creation is exactly equivalent or substantially equivalent to the prior art, the said invention or creation should be considered as lacking novelty, and should not be granted a patent.

With regard to said criteria for determining novelty, the Taiwan Supreme Administrative Court further explained in its 2015-Pan-No. 764 judgement of December 17, 2015 that, "When reviewing novelty issue in an invalidation case, the invention at issue recited in each claim shall be compared to single invalidation evidence, and the decision should be based on the contents publicly disclosed in the invalidation evidence. Such contents include the explicit disclosure and the implicit disclosure in the invalidation evidence.  The 'implicit disclosure' refers to the contents which can be directly and unambiguously obtained by the person having ordinary skill in the art from the common knowledge at the time when the invalidation evidence is disclosed.  In other words, although single invalidation evidence does not disclose all technical features contained in the patent at issue, the undisclosed part must be the absolutely indispensable part naturally inherited or existing in that invalidation evidence, and such undisclosed part is inevitably inherited in such invalidation evidence from the viewpoint of the person having ordinary skill in the art."  Conversely, "if the explicit disclosure and the implicit disclosure in the invalidation evidence are unable to disclose the technical features of the invention at issue, that invalidation evidence is unable to prove that the invention at issue lacks novelty."

In this case, the original court, the Intellectual Property Court, determined that there is only difference in the form of text description between the claim of the patent at issue and the prior art reference after comparing the technical features, and that the prior art reference is admissible to prove that related claims of the patent at issue lack novelty. However, the Supreme Administrative Court overruled this view and determined that, in addition to the difference in the form of text description, there is substantial difference in the components and structures between the patent at issue and the prior art reference.  Moreover, the difference not disclosed in the prior art reference is not naturally inherited or existing in that evidence.  Hence, the prior art reference is inadmissible to prove that Claim 1 lacks novelty.

From the above, it can be found that judicial practice considers that the explicit disclosure in the citation document is not the only evidence used for determining novelty of a claimed invention in a patent application.  The determination also includes the undefined content but naturally inherited or existing in the citation document in the view of the person having ordinary skill in the art. However, only when the "implicit disclosure" discloses the technical features of the invention at issue, can it be determined that the patent at issue lacks novelty.