ADR-007: Universal Share Prefix

[rootulp]

Description

ADR version of #659

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[evan-forbes]

Nice!! I like combining the two features into a single ADR, I might mention in the detailed design part that these are distinct features and can be implemented as such.

As we flesh this out, I look forward to your thoughts over what the new API will look like, and what our approach should be to handle that API change 🙂

[musalbas]

I don't have any strong opinions on naming as long as it's clear. That being said, I would consider compact shares to have one "message", which further reinforces the idea that data in reserved namespace follow the same share-level format as any other namespace.

[rootulp]

What is the definition of "message"? I interpreted it as the previous name for data that a user submits to be included in a block (i.e. the second message in MsgPayForMsg which was renamed MsgPayForData). Maybe in this context, "message" means something else because we're now using it to describe evidence, intermediate state roots, and transactions.

the idea that data in reserved namespace follow the same share-level format as any other namespace.

Agreed and I like the share-level format terminology. I think we can split the format into:

1. Share-level
   1. namespace
   2. info reserved byte
   3. [if info reserved byte has message start indicator=1] message length varint
2. Application-level
   1. For sparse shares: no additional format imposed
   2. For compact shares: 1 reserved byte for location of first unit in the share and every unit is prefixed with a varint of the unit's length

if this separation adds clarity

[liamsi]

Well written and accessible ADR. Left some nits. The proposed scheme is clear and it looks good to me.

[liamsi]

I think this is good to go :)