# World Structure

A world is a place you can change and inspect, with durable state beneath what you see.

## What Makes a World

A world keeps what exists, what agents do, and what the engine will accept as separate parts. One can change without replacing the others.

Content is the places, objects, and agents that belong to the world.

Decisions are what an agent does: a routine, a chosen model, or a recorded choice.

The engine is movement, checks, and world rules that stay valid.

A model proposes a decision. The engine decides whether that proposal can take effect. Rendered images, meshes, and splats show the world. They do not define every object’s identity or behavior.

## World, Version and Saved Entry

**World**

The owned place and the content that belongs to it. A workspace can hold several worlds.

**Version**

A specific authored state with objects, overrides, and edit history.

**Saved entry**

The title and references used to reopen a world and its authored version.

**State digest**

The exact state an edit is based on. Edits can advance state under the same version ID.

Keep both the world ID and the version ID when you build a client. A version ID alone is not a frozen copy of every later edit. Use its state digest to detect changes.

[Read a version](/docs/world-api/version)

## Keep Origins Distinct

A photograph is an observation. A reconstructed surface is an interpretation of its sources. A catalog placement is authored content. A simulated event is something that happened in a run. Sharing one place does not make these interchangeable.

A generated town does not establish that a real town existed. An agent’s behavior does not predict a real person’s choices.

[Assets and Imports](/docs/assets)

## State and Recorded Time

Authored edits change the place. Recorded decisions describe what its agents did over time. Replay reads those stored decisions without another model call.

Comparisons start their arms from the same saved state so a model change can be examined against a common starting point. Inspect the comparison definition and control before attributing differences to a model.

[Comparisons and Replay](/docs/comparisons)

## A Foundation for Larger Worlds

The composition design connects authored places, personal sources, and permitted imported content through identities and provenance. It leaves room for richer worlds without treating every visible detail as a separate canonical object.

General geographic extraction, arbitrary world rules, and a complete runnable import are not supported operations. Use the capabilities your installation reports for each world.

[Composition contract](https://github.com/twinkling-reality/exulanica/blob/main/docs/world-composition-contract.md)[Discover supported operations](/docs/world-api/capabilities)