> For the complete documentation index, see [llms.txt](https://guardian.hedera.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://guardian.hedera.com/docs/develop/guardian/standard-registry/policies/policy-creation/introduction/externaldatablock.md).

# extractDataBlock

This block is used for VC documents which are based on (or ‘conform to’) a schema which contains embedded schemas, extractDataBlock provides means to extract a data set which corresponds to any of these embedded schemas (at any depth level), and if required after processing to return the updated values back into the VC dataset to their original ‘place’.

## 1. Properties

| Property Name | Details                                                                                                                                                                 | Example                                                                                                                                                                                                    | Status |
| ------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------ |
| Action        | an action which is executed by the block                                                                                                                                | <p>o Get – find and extract the part of the document which corresponds to the specified schema</p><p>o Set – update the part of the document, which corresponds to the specified schema, with new data</p> |        |
| Schema        | the schema which is target of the action. It is used to identify the embedded part of the data object - i.e. the field in the document which corresponds to this schema | Contact Details (1.1)                                                                                                                                                                                      |        |

### 1.1 Extraction

<figure><img src="/files/h2azSBUUp5BUchw6k6qp" alt=""><figcaption></figcaption></figure>

### 1.2 Update

<figure><img src="/files/leMy29SIYaXQtHWxDe9L" alt=""><figcaption></figcaption></figure>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://guardian.hedera.com/docs/develop/guardian/standard-registry/policies/policy-creation/introduction/externaldatablock.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.