# Common Elements

All of the common elements used within this specification are described in this Document. Common elements include the data types, and their properties used in this specificaiton.

## Cardinality

All the variables in the specification will have a cardinality. The cardinality attribute defines the number of values allowed for the variable and whether the variables are ordered.

Supported types of cardinality are:

* *single*: only one value is allowed for the variable
* *multiple*: one or more values are allowed for the variable
* *ordered*: ordered list of values are allowed for the variable

## Data Types

### string

String data types should be used to represent string literal values.

### integer

Integer data types should be used to represent numbers without a fractional part.

### float

Float data types should be used to represent numbers with a fractional part.

### boolean

Boolean data types should be used to represent values with two states: true or false.

### uri

URI data types should be used to represent Uniform Resource Identifier (URI) reference values.

### map

Map data type should be used for variables whose values are key-value pairs. Map is a non-primitive data type with the following attributes.

| Attribute | Schema                                                     | Description                                                                                                           |
| --------- | ---------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------- |
| key       | dataType: *string*,   required: *true*                     | a map cannot contain duplicate keys and each key can map at most one value                                            |
| value     | dataType: *any*,   required: *false*, defaultValue: *NULL* | value can be of any other data type defined in QuML. value is optional and is by default set to NULL, if not provided |

### coordinate

Coordinate data type should be used to represent coordinates (x and y) of a single point in a canvas.

| Attribute | Schema                                | Description                     |
| --------- | ------------------------------------- | ------------------------------- |
| x         | dataType: *float*,   required: *true* | x-coordinate value of the point |
| y         | dataType: *float*,   required: *true* | y-coordinate value of the point |

### points

Points data type should be used for variables whose values represent an area on a canvas. Points are made up of a shape and the coordinates that define the boundary of the area.

| Attribute   | Schema                                                                                          | Description                                                                                            |
| ----------- | ----------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------ |
| shape       | dataType: *string*,   required: *true*,   range: *“point”, “circle”, “ellipse”, “poly”, “rect”* | represents the shape of points. it must be equal one of the predefined values defined in the range     |
| coordinates | dataType: *list of coordinate objects*,   required: *true*                                      | Coordinates should have at least one coordinate object. The number of coordinates depend on the shape. |

### media

Media data type should be used for representing a single media file. Media are re-usable to create assets which are used in questions and/or tests.

| Attribute | Schema                                 | Description                                                                                                                                                                                                   |
| --------- | -------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| id        | dataType: *string*,   required: *true* | identifier of the media object                                                                                                                                                                                |
| mimeType  | dataType: *string*,   required: *true* | technical mime type of the asset used by QuML players to understand the format of the asset. Supported types are image/png, audio/mp3, video/mp4, and video/webm                                              |
| mediaType | dataType: *string*, required: *true*   | type of the asset. this should be auto-derived from the mimeType value, current supported types are image, audio and video                                                                                    |
| src       | dataType: *string*, required: *true*   | path of the media file. QuML players will use this value to load all the media used in a question/test                                                                                                        |
| baseUrl   | dataType: *string*, required: *false*  | baseUrl of the server where the media is stored. Base URL can be used by QuML players to load media in a browser without CORS issues. this is achieved by QuML server proxying path to the provided base url. |


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