3.3 KiB
Metadata
Imagine you're searching for data on Spanish almond production within a dApp operating within the Ocean ecosystem, managed by a European fruit and nut association. This hypothetical dApp may host a vast collection of datasets, making it essential to have a way to identify the relevant ones. One effective approach is to have metadata associated with each dataset to serve as valuable information about the data itself.
Metadata plays a crucial role in asset discovery, providing essential information such as asset type, name, creation date, and licensing details. Each data asset can have a decentralized identifier (DID) that resolves to a DID document (DDO) containing associated metadata. The DDO is essentially JSON filling in metadata fields. To understand working with OCEAN DIDs, you can refer to the DID documentation. For a more comprehensive understanding of metadata structure, the DDO Specification documentation provides in-depth information.
In general, any dApp within the Ocean ecosystem is required to store metadata for every listed dataset. It's important to note that dApps do not necessarily need to possess the datasets themselves; they primarily focus on storing and managing the associated metadata. While specific metadata requirements may vary, certain fundamental pieces of metadata, including:
- name, e.g. “Largueta Almond Production: 1995 to 2005”
- dateCreated, e.g. “2007–01–20”
- datePublished, e.g. “2022–11–10T12:32:15Z”
- author, e.g. “Spanish Almond Board”
- license, e.g. “SAB Data License v4”
- price, e.g. “0”
- technical information about the files, such as the content type.
Other metadata might also be available. For example:
- categories, e.g. [“agriculture”, “economics”]
- tags, e.g. [“Europe”, “Italy”, “nuts”, “almonds”]
- description, e.g. “2002 Italian almond production statistics for 14 varieties and 20 regions.”
- additionalInformation can be used to store any other facts about the asset.
/**
* @dev setMetaData
* Creates or update Metadata for Aqua(emit event)
Also, updates the METADATA_DECRYPTOR key
* @param _metaDataState metadata state
* @param _metaDataDecryptorUrl decryptor URL
* @param _metaDataDecryptorAddress decryptor public key
* @param flags flags used by Aquarius
* @param data data used by Aquarius
* @param _metaDataHash hash of clear data (before the encryption, if any)
* @param _metadataProofs optional signatures of entitys who validated data (before the encryption, if any)
*/
function set metadata(uint8 _metaDataState, string calldata _metaDataDecryptorUrl
, string calldata _metaDataDecryptorAddress, bytes calldata flags,
bytes calldata data,bytes32 _metaDataHash, metaDataProof[] memory _metadataProofs) external {
require(
permissions[msg.sender].updateMetadata,
"ERC721Template: NOT METADATA_ROLE"
);
_setMetaData(_metaDataState, _metaDataDecryptorUrl, _metaDataDecryptorAddress,flags,
data,_metaDataHash, _metadataProofs);
}