This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.
The “one-way rule” is a key concept in determining inventorship differences for prior art purposes. According to MPEP 2136.04:
“The ‘one-way rule’ is that the inventorship of an application-publication having at least one inventor in common with the patent is different than the inventorship of the patent if the application-publication names at least one inventor who is not named in the patent.”
This rule simplifies the process of determining if there’s a difference in inventive entity, allowing for easier application of the “by another” criterion in 35 U.S.C. 102(e).