ActivityStreams Vocabulary Specification Guide

Complete reference to the ActivityStreams Vocabulary W3C Recommendation. This guide provides comprehensive documentation of the vocabulary used for describing social activities, objects, and relationships in the fediverse.

📋 Executive Summary

Purpose and Overview

The ActivityStreams Vocabulary is a W3C Recommendation (published May 23, 2017) that defines a comprehensive vocabulary for describing social activities, objects, and relationships in a machine-readable format. It serves as the foundational vocabulary for ActivityPub and other social web protocols.

Core Concepts:

Core Types: Essential base types (Object, Link, Activity, Collection)
Extended Types: Specialized types (Create, Follow, Like, Person, Note)
Properties: Attributes describing relationships and characteristics

Key Components

Objects

Content items, actors, and abstract entities

Activities

Actions performed by actors on objects

Links

References to external resources with metadata

Collections

Ordered or unordered groups of objects

🏗️ Core Types Architecture

Object

The base type for all ActivityStreams objects. Provides fundamental properties like id, type, name, and content.

Key Properties: id, type, name, content, url, published, updated

Link

Represents references to external resources with associated metadata and relationship information.

Key Properties: href, rel, mediaType, name, hreflang, height, width

Activity

Describes actions performed by actors. Extends Object with actor, object, and target properties.

Key Properties: actor, object, target, result, origin, instrument

Collection

Represents groups of objects or links, supporting both ordered and unordered collections.

Key Properties: items, totalItems, first, last, current

🎯 Extended Activity Types

Content Activities

Create: Creating new content
Update: Modifying existing content
Delete: Removing content
Announce: Sharing/boosting content

Social Activities

Follow: Following an actor
Like: Expressing approval
Block: Blocking an actor
Flag: Reporting content

Collection Activities

Add: Adding to collections
Remove: Removing from collections
Move: Moving between collections

👥 Extended Actor Types

Person

Individual human users in the social network

Organization

Formal organizations, companies, or institutions

Service

Automated services, bots, or applications

Group

Collections of actors working together

Application

Software applications that can perform activities

📄 Extended Object Types

Content Objects

Note: Short text content (like tweets)
Article: Long-form content with rich formatting
Document: File attachments and documents
Page: Web pages and standalone content

Media Objects

Image: Pictures and visual content
Video: Video content and streams
Audio: Audio files and podcasts

Social Objects

Event: Calendar events and gatherings
Place: Geographic locations
Profile: Actor profile information
Relationship: Connections between actors

🔗 Implementation in ActivityPub MCP Server

Vocabulary Usage

Our MCP server implements the complete ActivityStreams vocabulary to ensure full compatibility with the fediverse ecosystem.

Full support for all core and extended types
Proper JSON-LD context handling
Extensibility for custom properties
Validation against vocabulary specifications

LLM Integration

The vocabulary is exposed to LLMs through structured MCP tools and resources.

Type-aware object creation and manipulation
Vocabulary-guided content generation
Semantic understanding of social activities
Automated compliance checking