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Searching information in Data Marketplaces

Nevermined allows the creation of networks where multiple use cases can be built. The modular architecture of Nevermined allows that using the deployment of Smart Contracts, to have independent "domains" or "applications" using the same contracts.

As we detailed in the Nevermined Data page there is different kind of information generated in a Nevermined about the assets metadata and all the transactions happening in the Smart Contracts.

This information can be provided by the Marketplace API (off-chain Metadata) or the Graph (events emitted by Nevermined Contracts).

Here you can find a list of the most relevant search queries you can run:

Off-chain information: Metadata​

The Marketplace API uses Elastic Search to store the assets Metadata and some other Marketplace information (like bookmarks, user profiles, etc). The Marketplace API exposes an interface that allows to send complex queries using the Elastic search native format.

tip

You can find a full reference of the Elastic Search search options in their search documentation.

All the Metadata search queries can be sent using HTTP POST to the endpoint: http://marketplace-api/api/v1/metadata/assets/ddo/query

The following queries can be sent to the Marketplace API:

Search by asset name​

The main metadata attributes (like name, author, description, etc) are under the service.attributes.main object in the DDO/Metadata object. So for searching all the assets with a certain name you can run a query like this:

{
    "query_string": { 
        "query": "*My Search Query*", 
        "fields": ["service.attributes.main.name"] 
    }
}

Search by additional information​

The Additional Information section is an entry into the DDO/Metadata document where users can specify a free range of attributes. They can be domain specific, and the the marketplace can be used to search accross them. Things like categories:

{
    "match": {
      "service.attributes.additionalInformation.categories": "general"
    }
}

Search by price range​

The price is an attribute that is included in each of the services exposed in an asset. It is included as part of the service.attributes.main object. So to run a search using a range of prices could be something like this:

{
    "range": {
        "service.attributes.main.price": {
            "gte": "0",
            "lte": "500"
        }
    }
}

Sorting and paginating​

All the search queries can include sorting and pagination attributes:

{
    "query_string": { 
        "query": "*My Search Query*", 
        "fields": ["service.attributes.main.name"] 
    },
    "offset": "100",
    "page": "1",
    "sort": {
        "created": "asc"
    }

On-chain information: Smart Contracts​

The Nevermined Smart Contracts emit events when something is happening (typically a change of internal state). We developed some Nevermined Subgraphs that integrated with the The Graph Protocol allows the indexing of them for further searching. The different Nevermined Subgraphs are deployed in all the Nevermined public deployments. The Nevermined Subgraps expose a GraphQL interface that allows to send complex queries to fetch any information about what's happening in the Smart Contracts side.

tip

You can find a full reference of the The Graph search options in their search documentation.

All the Metadata search queries can be sent to the base endpoint: https://api.thegraph.com/subgraphs/name/nevermined-io/. The rest of the subgraph URL depends on:

  • The deployment tag name (i.e: public, common, etc)
  • The network name (i.e: mumbai, matic, mainnet, etc)
  • The contracts major version (i.e: v2)
  • The subgraph name coming from contract name (i.e: didregistry, whitelistingcondition)

Taking that into accout it can result in urls like:

Here you can find a list of the most relevant queries you can send to the Nevermined subgraphs:

On-chain information of an asset published​

Here you can see the AssetRegistered query about all the on-chain data emitted when an asset is registered:

query AssetRegistered {  
  didattributeRegistereds(
    where: {
      _did: "0xefdaacb570370f87f9a850c3e91e106e3ec17acee582bbba47cc03e7554616e5"
    }
  ){    
      id
      _did
      _owner
      _checksum,
      _value
      _lastUpdatedBy,
      _blockNumberUpdated    
  }
}

Assets published for a user​

In UserPublishedAssets query you can see all the information of assets published by a user:

query UserPublishedAssets {  
  didattributeRegistereds(
    where: {
      _owner: "0x322718d8defb7a58eddab138dededc582efa617f"
    }
  ){    
      id
      _did
      _owner
      _checksum,
      _value
      _lastUpdatedBy,
      _blockNumberUpdated    
  }
}

Assets purchased by a user​

In UserPurchasedAssets query you can see all the information of assets purchased by a user:

query UserPurchasedAssets {  
  fulfilleds(
    where: {
      _grantee: "0x827c6546ca48ee9a33efee3342292e61c6ea6507"
    }
  ){    
      id
        _agreementId
        _documentId
        _grantee
        _conditionId
  }
}

Downloads from a user​

In UserDownloads query you can see all the assets downloaded for a specific user:

query UserDownloads {  
  useds(
    where: {
      _agentId: "0x827c6546ca48ee9a33efee3342292e61c6ea6507"
    }
  ){    
      id
      _did
      _agentId
      _activityId
      provId
      _attributes
      _blockNumberUpdated    
  }
}

Transactions associated to an asset​

In AssetProvenance query you can get all the events associated with an asset:

query AssetProvenance {  
  provenanceAttributeRegistereds(
    where: {
      _did: "0xefdaacb570370f87f9a850c3e91e106e3ec17acee582bbba47cc03e7554616e5"
    }
  ){    
      id
      _did
      _agentId
      _activityId
      _attributes
      _blockNumberUpdated    
  }
}