# Group Schemas

## Linked Properties

| Link                | Description                              | Type          | Nullable | Supported operations |
|:-------------------:| ---------------------------------------- | ------------- | -------- | -------------------- |
| self                | This schema                              | Schema        |          | READ                 |

The schema provides more detailed information about the properties of a resource.
The schema is represented by a dictionary containing names of resource properties as keys
and objects describing the corresponding property as values.
These objects are called **field schema** and form the core of the schema representation,
each of them can contain its own `_links` and `_embedded` section.

# Field schema

## Linked Properties

| Property       | Description                                                    |
|:--------------:| -------------------------------------------------------------- |
| allowedValues  | List of resources that are assignable by the current user.     |

The `allowedValues` can either contain a list of canonical links or just a single link to a collection resource.
This is an optimization to allow efficient handling of both small resource lists (that can be enumerated inline) and large
resource lists (requiring one or more separate requests).

## Local Properties

| Property          | Description                                                                        | Type     | Default |
|:-----------------:| ---------------------------------------------------------------------------------- | -------- | ------- |
| name              | Human readable name of the property as it could be displayed in a UI               | String   |         |
| type              | The data type of the properties values                                             | MetaType |         |
| minLength         | The value of the property must at least contain the specified amount of characters | Integer  | 0       |
| maxLength         | The value of the property must at most contain the specified amount of characters  | Integer  | ∞       |
| regularExpression | The value of the property must match the given regular expression (if not null)    | String   | null    |
| required          | If true this property is not nullable                                              | Boolean  | true    |
| writable          | If false it is not allowed to **change** the properties value                      | Boolean  | true    |

All of the above properties that do not have a default value *must* be present in the schema.
For properties that have a default value, the client can assume the default value, if the property is missing.

Note that regular expressions used in the API follow the rules of [Ruby Regular Expressions](http://www.ruby-doc.org/core-2.1.5/Regexp.html).

## Example Schema [/api/v3/example/schema]

+ Model
    + Body

            {
                "_type": "Schema",
                "_links": {
                    "self": { "href": "/api/v3/example/schema" }
                },

                "lockVersion": {
                    "name": "Resource Version",
                    "type": "Integer",
                    "writable": false
                },
                "subject": {
                    "name": "Subject",
                    "type": "String",
                    "minLength": 1,
                    "maxLength": 255
                },
                "status": {
                    "_links": {
                        "allowedValues": [
                            { "href": "/api/v3/statuses/1", "title": "New" },
                            { "href": "/api/v3/statuses/2", "title": "Closed" }
                        ]
                    },

                    "name": "Status",
                    "type": "Status",

                    "_embedded": {
                        "allowedValues": [
                            {
                                "_links": { "self": { "href": "/api/v3/statuses/1" } },
                                "_type": "Status",
                                "id": 1,
                                "name": "New",
                                "position": 1,
                                "isDefault": true,
                                "isClosed": false,
                                "defaultDoneRatio": 0,
                                "createdAt": "2014-05-21T08:51:20Z",
                                "updatedAt": "2014-05-21T09:12:00Z"
                            },
                            {
                                "_links": { "self": { "href": "/api/v3/statuses/2" } },
                                "_type": "Status",
                                "id": 2,
                                "name": "Closed",
                                "position": 2,
                                "isDefault": false,
                                "isClosed": true,
                                "defaultDoneRatio": 100,
                                "createdAt": "2014-05-21T08:51:20Z",
                                "updatedAt": "2014-05-21T09:12:00Z"
                            }
                        ]
                    }
                }
            }

## view the schema [GET]

This is an example of how a schema might look like. Note that this endpoint does not exist in the actual implementation.

+ Response 200 (application/hal+json)

    [Example Schema][]