There are 13 types of attribute data types:
- Action attributes
- Boolean Attributes
- Color Attributes
- Date Attributes
- Dictionary Attributes
- File Attributes
- Font Attributes
- Interval Attributes
- List Attributes
- Number Attributes
- Set Attributes
- String Attributes
- URL Attributes
An Unsigned type is listed but not used or currently described, it should be regarded as experimental. Experimental attribute types appear from time to time and are usually adopted formally or removed; the release notes normally give detail on these types.
Note that Action, Color, File, Font, List, Set and URL data types are effectively all special forms of String attributes and share a common default: an empty string. Booleans default to false (which is not a string), Dates to 'never' and Numbers to 0 (zero).