Arguably the most important preparatory step to filing a patent application is a “patent search.” Ideally, such a search should seek out all relevant publications, because a patent examiner can cite any public document against any claim of invention. Since a pervasive search can be extremely expensive to conduct, however, the more commonly conducted patent search is primarily a review of all issued patents and published patent applications in order to determine what prior art exists that may be similar to the allegedly new invention. Such a search, of course, may still turn up references to other, non-patent public records.
Knowledge of prior art gained by a patent search, or by skill and experience in the field of the invention, helps to better define the novel aspects of the claimed invention as it is applied for. Such knowledge may also serve to save the inventor time and money pursuing previously claimed or otherwise unpatentable matter.
Also, the inventor has a duty to disclose, concurrent with filing a patent application, all that he or she knows about prior art in the field of the invention.