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Metadata
Marketplaces use the Metadata of the asset for discovery. Metadata consists of information like the type of asset, name of the asset, creation date, license, etc. Each data asset can have a decentralized identifier (DID) that resolves to a DID document (DDO) for associated metadata. The DDO is essentially JSON filling in metadata fields. For more details on working with OCEAN DIDs check out the DID concept documentation. The DDO Metadata documentation goes into more depth regarding metadata structure.
OEP8 specifies Ocean metadata schema, including fields that must be filled. It’s based on the public DataSet schema from schema.org.
Ocean uses the Ethereum mainnet and other compatible networks as an on-chain metadata store, i.e. to store both DID and DDO. This means that once the transaction fee is paid, there are no further expenses or devops work needed to ensure metadata availability into the future, aiding in the discoverability of data assets. It also simplifies integration with the rest of the Ocean system, which is Ethereum-based. Storage cost on Ethereum mainnet is not negligible, but not prohibitive and the other benefits are currently worth the trade-off compared to alternatives.
Due to the permissionless, decentralized nature of data on the Ethereum mainnet, any last mile tool can access metadata. Ocean Aquarius supports different metadata fields for each different Ocean-based marketplace. Developers could also use The Graph to see metadata fields that are common across all marketplaces.
Third-Party ERC20 Apps & Tools
The ERC20 nature of datatokens eases composability with other Ethereum tools and apps, including MetaMask and Trezor as data wallets, DEXes as data exchanges, and more. This post has details.