Citations represent added value from the patent office which we can use to help formulate better patent searches. Importantly, citations provide a language-independent search tool. This is of increasing importance in our global economy where applications are published around the world in many different languages. Links between cited references are now available in many databases free and fee-based and those links between patents related by subject can be exploited in a search to improve both relevance and recall. Cited references can provide access to older documents, which cannot be keyword searched or where terminology has changed.
In the patenting world references have been listed on patents granted at the United States Patent Office (USPTO) from February 1947 when examiners began citing references considered during the patent examination process. Previously cited references were available in the "File Wrapper" held at the USPTO.
One reason citation searching can be a powerful supplement to a keyword and classification based search is that citations introduce a language independent link between documents. A search using this link will almost certainly add relevant documents to the retrieved set. This can be very useful for increasing recall for prior-art, and competitive intelligence searches including patent landscaping and state of the art analysis.Prior-art Search
One of the most frequently performed patent searches is the "Prior Art" search. Using citations for this type of search can (a) reveal new terms (b) locate older patents where no text is available to search.
Additionally, cited references can take the search back further than text searching would allow (because there may be no abstracts available), and may also suggest additional keywords. Terminology usage changes with time and also with geographical location.
Another useful technique to build a prior art search is to find a heavily cited patent (also called a "key" or a "grandfather" patent). Today it is easy to locate a "key" or heavily cited reference using the PCI "Citing Reference Count" to rank results; caution over relevance is still encouraged according to the type of search undertaken.Competitive intelligence
Another frequently performed patent search is to find all patents by an individual inventor or an individual assignee. This may be an exercise on its own or part of a broader patent landscape. Using citations this type of search can also be expanded to review not only the target Assignee, but also those who have cited their patents.
Reviewing all citing patents will show competitors working on similar applications (but probably using different technology) and those using similar technology (but probably for different applications).
"IntellectPeritus search model considering citations of "all family members of ON target patents' as families are published at different times in different geography and hence count of citations for each family member gets varying based on filing and examining time of patent"
Above because cited references in patents may be added to the document for different reasons, at different times and by different people. A cited reference can be added by the inventor before filing or by the examiner during the patent examination process. Citations may also be added at other times during the life time of a patent by third parties either prior to grant or during the nine month post grant opposition period at the EPO.