# Listen to events

The events defined in the Relation Protocol are completely inherited from [EIP6239](http://eips.ethereum.org/EIPS/eip-6239), we need to listen to all events that comply with the EIP6239 specifications:

```solidity
/**
 * @title Semantic Soulbound Token
 * Note: the EIP-165 identifier for this interface is 0xfbafb698
 */
interface ISemanticSBT {
    /**
     * @dev This emits when minting a Semantic Soulbound Token.
     * @param tokenId The identifier for the Semantic Soulbound Token.
     * @param rdfStatements The RDF statements for the Semantic Soulbound Token. An RDF statement is the statement made by an RDF triple.
     */
    event CreateRDF (
        uint256 indexed tokenId,
        string rdfStatements
    );
    /**
     * @dev This emits when updating the RDF data of Semantic Soulbound Token. RDF data is a collection of RDF statements that are used to represent information about resources.
     * @param tokenId The identifier for the Semantic Soulbound Token.
     * @param rdfStatements The RDF statements for the semantic soulbound token. An RDF statement is the statement made by an RDF triple.
     */
    event UpdateRDF (
        uint256 indexed tokenId,
        string rdfStatements
    );
    /**
     * @dev This emits when burning or revoking Semantic Soulbound Token.
     * @param tokenId The identifier for the Semantic Soulbound Token.
     * @param rdfStatements The RDF statements for the Semantic Soulbound Token. An RDF statement is the statement made by an RDF triple.
     */
    event RemoveRDF (
        uint256 indexed tokenId,
        string rdfStatements
    );
    /**
     * @dev Returns the RDF statements of the Semantic Soulbound Token. An RDF statement is the statement made by an RDF triple.
     * @param tokenId The identifier for the Semantic Soulbound Token.
     */
    function rdfOf(uint256 tokenId) external view returns (string memory);
}
```

* CreateRDF: Triggered when a SBT containing RDF semantics is created.
* UpdateRDF: Triggered when a SBT containing RDF semantics is updated.
* RemoveRDF: Triggered when a SBT containing RDF semantics is removed.

By listening to these events on the blockchain, you will receive RDF data containing semantics (code 7-1), which contains user behavior data.

{% code title="code 7-1" %}

```
:Soul_0x0109c8ee3151bde7b6b5d9f37e9d2c4bc16930fe p:following :Soul_0x6247123ec0fe0d25feb811e3c4d4a760c1f2e63e .
```

{% endcode %}

## Use The Graph index

With [The Graph](https://thegraph.com/), we can index users' behavioral data on the blockchain easily. You can refer to [The Graph documentation](https://thegraph.com/docs/en/developing/creating-a-subgraph/).

Below is the behavioral data from the Polygon network through our listening. The address is:

<https://thegraph.com/hosted-service/subgraph/relationlabs/semantic-sbt>

* Query via the playground provided by The Graph:

<figure><img src="https://2101283974-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FYeYon1a8IZta2Zm96hF1%2Fuploads%2Fgit-blob-b6757bef7972501c9d4ae7a82d591c427b0b72d2%2Fthe-graph-playground.png?alt=media" alt=""><figcaption><p>Figure 7-2 Query via the playground</p></figcaption></figure>

* Query via the GraphQL API provided by The Graph:

eg. To query the latest two token records:

{% code overflow="wrap" %}

```shell
curl --location --request POST 'https://api.thegraph.com/subgraphs/name/relationlabs/semantic-sbt' \
--header 'Content-Type: application/json' \
--data-raw '{"query":"{\n  turtles(first: 2) {\n    id\n    owner\n    tokenId\n    turtle\n  }\n}"}'
```

{% endcode %}

The result

{% code overflow="wrap" %}

```shell
{"data":{"turtles":[{"id":"33456276423","owner":"0x16ff7821a8d293cd2ea07b650fc69ea9206d0615","tokenId":"1","turtle":":Activity1 p:name \"Activity_2049_1\" . :Activity1 p:level 1 . "},{"id":"33456276425","owner":"0x16ff7821a8d293cd2ea07b650fc69ea9206d0615","tokenId":"2","turtle":":Activity2 p:name \"Activity_2049_2\" . :Activity2 p:level 2 . "}]}}
```

{% endcode %}

## Use The ethers.js

[ethers.js](https://github.com/ethers-io/ethers.js) is a JavaScript library for interacting with the Ethereum Blockchain and its ecosystem.

For example:

```javascript
const ethers = require('ethers')
const rpc = 'https://polygon-mumbai.blockpi.network/v1/rpc/public'
let abi = ['event CreateRDF(uint256 indexed tokenId, string rdfStatements)']
const provider = new ethers.JsonRpcProvider(rpc)
const iface = new ethers.Interface(abi)
const filter = {}

// listen
provider.on(filter, (e) => {
  try {
    let event = iface.parseLog(e)
    console.log(event)
    // parse ...
  } catch (error) {}
})
```