# `Doi`

A digital object identifier, naming a paper or a dataset: `10.1038/nphys1170`.

Use it to cite publications. For a person, use [`Orcid`](/docs/types/type-orcid.md).

## Shape

One value, held as text in one set form, with no parts: `10.1000.10/123456`.

## Example

```jadpo
Doi("10.1038/nphys1170")
```

`Doi(raw)` checks the text, and text that isn't one breaks the `format` rule.

`text.parse(raw, as: Doi)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `doi:10.1000/182`, `https://doi.org/10.1000/182` or `10.1038/NPHYS1170`.

## Good to know

- It has no resolver in front, so `doi:` and `https://doi.org/` are refused.
- `==` tells you whether two are the same. `<` and `list.sort_by` don't take it.

## In JSON

A string, in a request, a response or `json.write`:

```json
"10.1000/182"
"10.1038/nphys1170"
"10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o"
```

## Details

<details>
<summary>Text form, storage, how it is shown, and operations</summary>

`Doi` is in the group Software, and has been in Jadpo since 0.1.0.

### Text form

`text.from` writes one standard text form, the same form `text.parse` reads back: `10.1000/182`, `10.1038/nphys1170` and `10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o`.

### How it is stored

It is stored in one column named for the field, of type `text`. `10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o` is stored as `'10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o'`.

### How it is shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `10.1000/182` | `10.1000/182` |
| `10.1038/nphys1170` | `10.1038/nphys1170` |
| `10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o` | `10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o` |
| `10.1000.10/123456` | `10.1000.10/123456` |

### Operations

It also takes `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. [How every standard type behaves](/docs/every-standard-type-meets-one-contract.md) says how they work.

</details>