isoc is yet another "standard" container format.
It brings together the best bits of Docker Image Specification 1.0 and App Container Specification 0.3.0+git into a comprehensive yet portable container archive format, at the cost of a "few" duplicated bytes.
An isoc image is a appc image embedded in a docker image, but also a docker image embedded in a appc image. Some people might describe it as an iso-contained container format.