This specification describes a framework for an interchange format to address the current and future needs of additive manufacturing technology. For the last three decades,the STL file format has been the industry standard for transferring information between design programs and additive manufacturing equipment. An STL file contains information only about a surface mesh and has no provisions for representing color, texture, material, substructure, and other properties of the fabricated target object. As additive manufacturing technology is quickly evolving from producing primarily single-material, homogenous shapes to producing multimaterial geometries in full color with functionally graded materials and microstructures, there is a growing need for a standard interchange file format that can support these features.