> For the complete documentation index, see [llms.txt](https://docs.fractalworks.io/joule/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fractalworks.io/joule/concepts/key-joule-data-types/contextual-data.md).

# Contextual data

## Overview

[Contextual data](/joule/components/contextual-data.md) provides additional context to support advanced stream processing use cases.

Joule offers a base implementation for storing contextual data elements, enabling the **development of custom components** that are both **efficient and flexible** in processing external data within the platform.

The `ReferenceDataObject` extends the `HashMap<String, Object>`, providing the **full benefits of a map structure** while adding extensions specifically designed for **storing and querying** contextual data.

This data structure allows for **seamless integration and management of contextual information** across Joule's platform.

## Key features

1. <mark style="color:green;">**Extends HashMap**</mark>\
   Inherits all features of `HashMap<String, Object>`, offering a flexible key-value data structure.
2. <mark style="color:green;">**Contectual data storage**</mark>\
   Designed for storing and querying contextual reference data efficiently.
3. <mark style="color:green;">**Custom data representation**</mark>\
   Supports storing and retrieving custom data, providing flexibility for various use cases.

## Build with the SDK

{% content-ref url="/pages/fBCARp3hs0REBtAX9rzX" %}
[ReferenceDataObject](/joule/developer-guides/builder-sdk/data-types/referencedataobject.md)
{% endcontent-ref %}