> ## Documentation Index
> Fetch the complete documentation index at: https://docs.truemath.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Creating a domain
> Create a new calculation domain — set its title and description, build it up from activities and variables, and import, export, copy, or archive it.
A [domain](/concepts/domains) is the self-contained model you author and target when you run a calculation. Creating one gives you a **draft** — a working copy you build up and later publish. Calculations only ever run against the published version, so a new domain is yours to shape until you decide it is ready. See [Versioning](/concepts/versioning).
## What you set when you create a domain
* **Title and description** — human- and agent-readable labels. The description is more than display text: clear, precise descriptions improve natural-language and agent results. Write it precisely, the way you would write the one line a search engine will index.
* **Identity** — TrueMath assigns a stable unique identifier (UUID) (the `domain_id` you pass to the [API](/api/calculate)) and a stable **key**. You do not choose these; they identify the domain for as long as it exists. The UUID is how you reference the domain through the API; the key is how TrueMath recognizes the same domain across accounts when you [copy](#copy-to-another-account) it. The key is not part of a domain's exported definition. See [Managing a domain](#managing-a-domain) and [Domains](/concepts/domains#identity-and-versions).
## How a domain takes shape
A domain is a set of [activities](/concepts/activities) and the [variables](/concepts/variables) they relate. You build it from the activities outward:
1. **Write activities.** Each activity is an equation that relates a set of variables. See [Writing activities](/authoring/writing-activities).
2. **Write the equations.** The expression syntax — literals, operators, functions, and units. A variable first comes into being when an equation references it. See [Writing equations](/authoring/writing-equations).
3. **Define the variables.** Configure each variable's display, default, and unit. See [Defining variables](/authoring/defining-variables).
4. **Add tables and charts** where a variable holds more than one value or is presented visually. See [Tables](/authoring/tables) and [Charts](/authoring/charts).
5. **Test and publish.** Verify the domain calculates as expected, then publish the draft. See [Testing and publishing](/authoring/testing-and-publishing).
## Where a domain starts
* **From scratch** — an empty draft you build up from your own activities and variables.
* **From a library domain** — start from a pre-built domain and adapt it to your conventions and business logic. See [Customizing a library domain](/authoring/customizing-a-library-domain) and the [Domain library](/domain-library/overview).
* **From a JSON definition** — import an existing [domain definition](/authoring/domain-definition). See [Managing a domain](#managing-a-domain).
## Managing a domain
Beyond editing its activities and variables, a domain can be exported, imported, copied, and archived. A domain's exported definition carries its activities and variables, but not its identity — neither the UUID nor the [key](#what-you-set-when-you-create-a-domain). Identity matters when you **copy** a domain between accounts: the copy shares the source's key (under its own UUID in the destination), which is how TrueMath recognizes the two as the same domain and updates the copy in place rather than duplicating it.
### Export and import JSON
A domain's full definition can be **exported as JSON** — the complete set of activities and variables, ready to copy. See [The domain definition](/authoring/domain-definition) for the structure of that JSON.
**Importing** accepts a pasted JSON definition and shows a comparison of the changes against the domain you are importing into before you accept them, so you can review exactly what an import will add, remove, or alter rather than applying it blind. An import overrides the domain you selected: the definition carries no key, so it is your selection — not anything in the JSON — that determines which domain is replaced.
### Copy to another account
If you belong to more than one account, you can **copy a domain to a different account**. This is how a domain authored in one account is brought into another. The option is available to the domain's owner. The copy shares the source domain's key but takes its own UUID in the destination account, so copying the same domain again later updates that copy rather than creating a second one — the key is what TrueMath matches on to recognize the two as the same domain.
### Archiving
**Archiving** retires a domain and hides it from use, the final stage of the domain [lifecycle](/concepts/versioning). An archived domain is no longer returned by the [API](/api/domains) or available in the [Playground](/playground/tour).
There is currently no interface for reviewing or recovering archived domains. Archive a domain only when you are sure you no longer need it.
A draft is not usable for calculations until it is published. Only published domains are returned by the [API](/api/domains) and available in the [Playground](/playground/tour). See [Testing and publishing](/authoring/testing-and-publishing).