We need a way to store/represent parts in a 3MF independent of a build

[martinweismann]

Currently, "A consumer MUST NOT output any 3D objects not referenced by an element" (should actually say "...referenced directly or indirectly via components objects...").
https://github.com/3MFConsortium/spec_core/blob/master/3MF%20Core%20Specification.md#343-build-instructions

This makes it hard/impossible to use 3MF as a simple representation of mesh data (e.g. like an STL) independent of a build.

[martinweismann]

On a similar note (from @atardugno):
The way 3MF defines the coordinate system requires an "output field" of a device.
When 3MF is used not in the concept of 3D printing, there is no output field, and also not the coordinate system defined by it. We need to allow for this in the spec.
https://github.com/3MFConsortium/spec_core/blob/master/3MF%20Core%20Specification.md#31-coordinate-space