PCT International Search and Preliminary Examination Guidelines
15.18 The international search is essentially a thorough, high quality, search of the most relevant resources, and the report serves to provide information on the relevant prior art to the applicant, to the public if the international application is published and to the designated Offices and the International Preliminary Examining Authorities.
15.19 In some instances there are no facilities for systematic searching by the designated Offices. The examiner should, therefore, assume that the designated Offices are dependent on the work of the International Searching Authorities for their knowledge of the state of the art on which their assessments of the patentability of the claimed invention will be based.
15.20 Nevertheless, it must be realized that, even though completeness should be the ultimate goal of the international search, this goal may not be necessarily obtained, because of such factors as text search limitations and the inevitable imperfections of any classification system and its implementation, and may not be economically justified if the cost is to be kept within reasonable bounds. The examiner therefore considers the most relevant search resources for the technology, including databases listed in the Search Guidance Intellectual Property Digital Library (IPDL) (available through the WIPO web site at www.wipo.int), and organizes the search effort and utilizes the search time in such a manner as to reduce to a minimum the possibility of failing to discover existing highly relevant prior art, such as complete anticipations for any claims. For less relevant prior art a lower retrieval ratio is acceptable.