Recently, the Open Container Intiative announced the new Image Spec Format project, an expansion of the OCI Runtime Spec project, which set rules on how to run containers. The Image Spec Format aims to provide users with rules on how container images should be built, focusing mostly on serialization, security (hasning and signing), and federated naming.
According to the Initiative's GitHub page, the project was started because:
We are seeing many independent implementations of container image handling including build systems, registries, and image analysis tools. As an organization we would like to encourage this growth and bring people together to ensure a technically correct and open specification continues to evolve reflecting the OCI values.
The long term goal is to introduce the ability to run containers across a variety of runtimes, which will be achieved in combination with the Runtime Spec project. The Image Spec Format project is based on Docker 2.2 (which in turn is heavily influenced by the appc spec), and is supported by a variety of vendors including Docker, Mesosphere, Rancher Labs, VMware, Dell, and Red Hat. You can find the full press release here, and find the Image Spec Format GitHub page here.