GLTF for standalone material files

I'm just starting to look into the GLTF spec, and so far I approve of most of the design decisions. One thing I am not seeing is whether the format supports / is meant to support standalone material files. There are many situations when a material should be shared by multiple model files or just kept as a standalone asset the user can load programmatically. Considering how bad the state of cross-application materials is in the game industry, this seems like a golden opportunity. I was disappointed to see that Substance Designer does not export materials in GLTF format. It seems that the spec designers think of a material as being a bunch of settings attached to a model.

If it's conceivable, I would like to replace our model and material files entirely with GLTF.

What can you tell me about this?

Start by reading the glTF specification's treatment of materials and how assets are shared across model files. Determine whether standalone material files are supported or would require a specification change, and document the resulting guidance or proposal.

Written by the indexing model from the issue text.