> ## Documentation Index
> Fetch the complete documentation index at: https://help.dingtalk.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Document data structure

> A DingTalk Docs document is a tree of BlockElement nodes whose nestable child types vary by block, for example callout blocks accept any BlockElement while paragraph blocks accept only InlineElement.

An online document is a tree composed of multiple block elements. Different types of `BlockElement` can nest different element types. For example, a `highlight block` can nest any `BlockElement`, while a `paragraph block` can only nest `InlineElement`. The overall structure of a document is as follows:

Take this document as an example. The page can be broken down as follows: