nips/62.md

NIP-62
======

Collections
----------

`draft` `optional`

This NIP defines the minimum specification for collections - ordered, optionally-hierarchical assemblies of nostr events. Collections provide a standard way to organize and present related content, similar to how books organize chapters or journals organize articles.

## Event Kinds

This NIP defines two primary event kinds:

- `30040`: Collection Index
- `30041`: Collection Section

## kind 30040: Collection Index

A collection index defines the structure and metadata of a collection. It serves as a table of contents that references the actual content sections.

### Requirements

- The `content` field MUST be empty
- MUST include a `title` tag containing the full title of the collection
- MUST be uniquely identifiable by the combination of:
  - `d` tag
  - `pubkey`
  - `kind` (30040)
- MUST include `e` tags listing the events in desired display order
  - Referenced events SHOULD be kind 30041 sections or nested kind 30040 indices
  - Additional event kinds MAY be supported
- For derivative works:
  - MUST include a `p` tag identifying the original author
  - MUST include an `E` tag referencing the original event immediately after the `p` tag

### Example Index

```json
{
    "id": "<event_id>",
    "pubkey": "<event_originator_pubkey>",
    "created_at": 1725087283,
    "kind": 30040,
    "tags": [
        ["d", "aesop's-fables-by-aesop"],
        ["title", "Aesop's Fables"],
        ["author", "Aesop"],
        ["i", "isbn:9780765382030"],
        ["t", "fables", "classical", "literature"],
        ["published_on", "2003-05-03"],
        ["published_by", "public domain"],
        ["image", "https://imageserver.com/piclink.jpg"],
        ["summary", "Collection of selected fables from the ancient Greek philosopher, known as Aesop."],
        ["e", "<id>", "<relay_url>", "<pubkey>"],
        ["e", "<id>", "<relay_url>", "<pubkey>"],
        ["p", "<pubkey_0>"],
        ["E", "<original_event_id>", "<relay_url>", "<pubkey>"]
    ],
    "sig": "<event_signature>"
}
```

## 30041: Collection Section

Sections (also known as zettels, episodes, or chapters) contain the actual content that makes up a collection.

### Requirements

- MUST include a `d` tag
- MUST include a `title` tag describing the section (e.g., "Introduction", "Chapter 1", etc.)
- The `content` field:
  - MUST contain text meant for display to the end user
  - MAY contain AsciiDoc markup
  - MAY contain wikilinks (denoted by double brackets)

### Example Section

```json
{
    "id": "<event_id>",
    "pubkey": "8ae74c618a4713f32129...",
    "created_at": 1708083476,
    "kind": 30041,
    "tags": [
        ["title", "The Farmer and The Snake"],
        ["d", "aesop's-fables-by-aesop-the-farmer-and-the-snake"],
        ["wikilink", "fables", "ad9dad8c4006d781d94ae001884b6987caa2a6852f3f43a571ca6838d0ced3af", "wss://thecitadel.nostr1.com"]
    ],
    "content": "== The Farmer and The Snake\nA [[fable]], by Aesop.\nONE WINTER a Farmer found a Snake stiff and frozen with cold. He had compassion on it, and taking it up, placed it in his bosom. The Snake was quickly revived by the warmth, and resuming its natural instincts, bit its benefactor, inflicting on him a mortal wound. 'Oh,' cried the Farmer with his last breath, 'I am rightly served for pitying a scoundrel.'\nThe greatest kindness will not bind the ungrateful.",
    "sig": "49cab8c75fb35cec71d07258..."
}
```

## Extensions

Collections are flexible and can be extended for different types of content. Examples include:

- Books
- Academic journals
- Course materials
- Documentation

Additional tags relevant to the specific content type MAY be included in both index and section events.