Design the Block Data Model

Problem

Design Notion's core abstraction: the block model where everything (text, page, table, toggle) is a block.

Requirements

• A block has type, content, parent, ordered children
• Move/insert/delete blocks
• Different render behavior per type
• Permissions inherited from ancestors

What evaluators look for

• Uniform block interface with type-specific behavior
• Ordering of children (fractional indexing)
• Reference vs containment

Extension

Support a block appearing in multiple places (references/mentions).