XCM Asset Metadata

[mrshiposha]

This is a refined version of the XCM Asset Metadata RFC.

This PR supersedes the PR opened in the xcm-format repository following the migration of XCM RFCs to the Fellowship RFCs.

Summary

This RFC proposes a metadata format for XCM-identifiable assets (i.e., for fungible/non-fungible collections and non-fungible tokens) and a set of instructions to communicate it across chains.

[acatangiu]

Looks good to me!

[xlc]

Maybe explicit define MetadataMap and MetadataKeys

type MetadataKey = Vec<u8>;
type MetadataValue = Vec<u8>;
type MetadataMap = BTreeMap<MetadataKey, MetadataValue>;
type MetadataKeys = BTreeSet<MetadataKey>; // or call it MetadataKeySet?

[xlc]

Let me know if you want me to put this for onchain voting

[franciscoaguirre]

You're envisioning this metadata to be useful for fungible assets as well? In that case, would it be something small like name, decimals, symbol?

If that's the case, I guess we only need to have this security measure for NFTs. Runtimes should identify foreign NFTs and not report the metadata for them since they don't hold the source of truth.

[mrshiposha]

You're envisioning this metadata to be useful for fungible assets as well? In that case, would it be something small like name, decimals, symbol?

Yes, since Asset { id: ASSET_ID, fun: NonFungible(AssetInstance::Undefined) } now means a collection.
However, we'd need some standards so different fungible implementations could report something universally applicable.

If that's the case, I guess we only need to have this security measure for NFTs.

What about the derivative fungible collections? They might also have a symbol, decimals, etc. However, other chains shouldn't use derivative collections' information as true information (though maybe they might want to inspect such information?).

Runtimes should identify foreign NFTs and not report the metadata for them since they don't hold the source of truth.

True. Yet, a counterparty might act maliciously. I wrote this safety note just to highlight that it is our decision on whom to trust.

[franciscoaguirre]

I'm wondering if there are any metadata keys that we can make known and standard instead of leaving everything as a Vec<u8>. But I think this is a good start and cross-chain NFT standards can start to emerge from this.

[mrshiposha]

Yes, metadata standards should exist. This is one of the tasks of the NFT Collective (a project launched by Unique Network).
However, this RFC outlines the technical possibility of interchanging data in a universal way via XCM.

[mrshiposha]

@xlc Could you please put this RFC for on-chain voting?

[xlc]

/rfc propose

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Hey @xlc, here is a link you can use to create the referendum aiming to approve this RFC number 0125.

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It is based on commit hash d16c0f71119a168e1be0cc4845902658c9ccaad2.

The proposed remark text is: RFC_APPROVE(0125,7e5c5f974903fc550ec31aa565177f22675f1238255dd5d7c89561d33b654b49).

[xlc]

Referenda https://collectives.subsquare.io/fellowship/referenda/275

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