Best Practices for Performing Comprehensive Assignee Searches – from intellogist.com
This post was guest-authored by Kristin Whitman of Intellogist.com, a free web resource and online community for patent and prior art searching.
Finding patent documents that are owned by a given corporation of interest is often referred to as “assignment searching,” because the owner of a patent is formally called the “assignee” in the US patent system. There are several major obstacles that can prevent searchers from finding documents that are assigned to a given corporation of interest; performing a simple search on the corporation’s name in a given patent database will often yield only partial results.
One major obstacle to this kind of searching is that assignment data may not be printed on the document face at the time of publication, and thus may not be available in certain electronic databases. This scenario is extremely common for US published patent applications, as applicants do not have to include this assignment information when patents are filed. Finding these “hidden” documents can be critical to a search project. Strategies to combat this obstacle include:
- Search the Agent/Correspondent field – Sometimes the name of the company will be in the “representative,” “agent,” or “correspondent” field of the patent.
- Search the assignment data which appears in various patent legal status databases – Sometimes this data will not appear on a published application’s face, but will be included in that country’s re-assignment records.
- Search a database organized by patent family - Even if the search is for US patent documents only, searchers should expand to other non-US collections rather than limiting the search to US results. This kind of search may find non-US family members held by the assignee of interest, allowing searchers to infer that the company may possibly hold the US family member as well.
Search a database that predicts probable owners – Some patent databases use special logic to predict probable assignees for unassigned patents – for example, algorithms can check the representative/agent field to look for a corporate address, or may check the inventor field to see if a well-known corporate inventor suddenly has a patent application upon which his or her company name does not appear. Innography and IFI Claims are two examples of databases which can make this type of prediction.
Another obstacle that arises in assignment searching is that the company name may have multiple variant spellings, and/or may have been transliterated to or from a language that does not use Latin characters. This concern will affect almost every assignee and inventor name; the reality is that no company name can totally escape from misspellings when it is represented on patent documents, and that any patent which is filed internationally may have the company and inventor names transliterated into other languages. Strategies to combat this problem include using a search engine with a “browse index” or “expand” feature to show index entries with similar spellings, such as PatBase or STN, or using a search database that offers standardized assignee names, such as the DWPI fileHYPERLINK “” , or IFI Claims. Further, to ensure that an assignment search covers all of the corporate divisions that are of interest, a corporate tree database may be used to identify subsidiary names.
Finally, it is possible that a search will miss documents that may have been re-assigned to the company of interest, due to the possibility that only original ownership data may be contained in the chosen database. To combat this possibility, searchers can extend their search by querying re-assignment databases and legal status registers for the countries of interest. In addition, the INPADOC legal status database is another source for re-assignment information for certain countries, although its coverage is dependent upon self-reporting from the national patent offices.
For more in-depth information on any of these options, please see the Best Practices article on Assignment Searching hosted on Intellogist, your source for expert answers to your patent search questions. If you are a newcomer to prior art searching, see the General Searching best practices wiki article to learn about basic search techniques which are broadly applicable to many types of searches. In addition, Intellogist also offers specialized techniques which may be applied to validity or infringement searches.
In addition, if you’d like to learn more about being an effective prior art searcher, you might like to consider one of the upcoming Advanced Courses from Patent Resources Group, The Art and Science of Patent Searching.





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