Under what circumstances is an interference file available according to MPEP 100?

An interference file is available when it includes a patent or published application. This is because the purpose of an interference proceeding is to resolve disputes regarding the priority of inventions claimed in different applications or patents. When a dispute arises, the relevant documents, which may include pending applications, patents, or published applications, are made available to help determine who has the rightful claim to the invention.

The existence of a patent or published application in the interference means that there is a public record detailing the claims and the specifics of the inventions involved, which is essential for conducting a thorough examination of the claims made by the parties in the interference. This availability allows for transparency and helps ensure that all parties have access to the necessary information to argue their case effectively.

Regarding the other options, an interference involving only a pending application may lack the comprehensive public documents necessary to fully assess the claims. Similarly, expired patents and an agreement among inventors do not inherently ensure that a sufficient record exists to support an interference proceeding's evaluation. This highlights the importance of having a patent or published application as part of the interference file.