same subject matter are filed, only the party who filed first will be entitled to a patent under the "first-to-file rule". Until the enactment of the America Invents Act, the United States followed a first-to-invent rule, under which early filing may prevent the use of certain materials from being applied against the patent application as prior art while the patent application is pending before the patent office. However, three consecutive congressional sessions in the United States from 2005-2009 have attempted to change the United States to the first-to-file rule with the Patent Reform Act of 2005, the Patent Reform Act of 2007, and the Patent Reform Act of 2009. Finally, on September 16, 2011, the United States shifted to the first-to-file rule with the enactment of the America Invents Act. Filing an application Most patent applications have at least two components, including a general, written description of the invention and at least one "embodiment" thereof, and a set of "claims," written in a special style that defines exactly what the applicant regards as the particular features of his or her invention. These claims are used to distinguish the invention from the existing prior art, and are compared by the patent office to the prior art before issuing a patent. Patent applications in most jurisdictions also usually include (and may be required to include) a drawing or set of drawings, to facilitate the understanding of the invention. In some jurisdictions, patent models may also be submitted to demonstrate the operation of the invention. In applications involving genetics, samples of genetic material or DNA sequences may be required. Search and examination The search and examination phases constitute the main part of the prosecution of a patent application leading to grant or refusal. A search is conducted by the patent office for any prior art that is relevant to the application in question and the results of that search are notified to the applicant in a search report. Generally the examiner conducting the search indicates in what aspect the documents cited are relevant (novelty, inventive step, background) and to what claims they are relevant. The materials searched vary depending on the patent office conducting the search, but principally cover all published patent applications and technical publications. The patent office can provide a preliminary, non-binding, opinion on patentability, to indicate to the applicant its views on the patentability and let the applicant decide how