The US Patent Office has issued rejection guidelines. You can read them in the Federal Register link here or read K.C. Jones summary link here. Here is my attempt to boil it down. "Factual inquiries" remain the basis for deciding whether a proposed patent is obvious. "That is, patent examiners will continue to consider the scope and content of the prior art, the differences between the claimed invention and the prior art, the level of ordinary skill in the pertinent art, and objective evidence relevant to the issue of obviousness," according to John Doll, commissioner for patents. Patent examiners must explain their rejection of an application as being obvious. One basis is if the examiner identifies a prior art teaching, suggestion, or motivation, but such a basis is not essential to determining whether an invention is obvious. The guidelines include examples.