As a first approximation, the URI scheme might be something like:
swh:VERSION:OBJECT_KIND:OBJECT_ID
with more specific instances like:
- swh:1:content:SHA1 (for blobs)
- swh:1:revision:SHA1 (commits)
- swh:1:directory:SHA1 (directory trees)
- swh:1:release:SHA1 (tags)
- etc.