Search strategy and queries

A number of test cases were designed for assessing the different databases.  Eight US or EP utility patents or PCT patent applications in different art areas (chemistry / biotechnology; mechanical; electrical) and a design patent were chosen to represent technologies on which extensive searches were conducted, while up to five additional cases were used for more in-depth study of sites that claim to use divergent search technology. For non-US patents, each of the documents had an associated search report that could be utilised as one measure of whether the use of a particular database found the same prior art that a European examiner would have noted.

It is useful to remember that the claims in the original patent application may not bear resemblance to the claims in the issued patent.  Rather than focus on claim structure, the approach of an examiner is to determine the inventive concept and base a search on that.

In general, a patent examiner will approach finding prior art by a combination of IPC designation(s) (US classifications for examiners at the USPTO) or ECLA (EPO) classifications, keywords, and the inventor names.. The latter are important because invalidating prior art is most often found in public disclosures by the inventors.

The public technology searcher is more likely to bypass the use of classifications, but may add the use of assignee/applicant names and may be able to use keywords in a way that reflects more in-depth field-specific knowledge.

Classification codes are assigned precisely on the basis of the technology field of the invention; this is where related art will be most likely found.  Thus, for each of these patent documents, the initial search for examiners used the primary IPC.  As expected, too many results were returned.  Further refinement of the search used keywords.  Given the amount of time examiners are generally allowed for a search, USPTO examiners tend to target obtaining 50-100 results.3 Titles, abstracts, and, at times, drawings are scanned to target the relevant documents.

Though searches on classification codes typically returned more documents than were relevant, in some fields of art they failed to find the most relevant documents.  For example, inventions that are part of “nanotechnology” may contain elements of different art areas.  To improve the ability to search and examine nanotechnology-related patents, a new cross-reference digest (to be eventually replaced by a classification schedule) has been established by the USPTO and other patent offices may follow suit, but no patent or application has yet been assigned to the new classification.   Nano-scale objects themselves are not new, and for our main example case, US6689338 (“Bioconjugates of nanoparticles as radiopharmaceuticals”), searches using “nano*” in combination with the classification of the main inventive subject matter do find patent documents that appeared to be highly relevant in many of the databases.


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