All Tinderbox attributes use a specific data types. If not the author of the document, there are ways to determine an attribute's data type. In general descriptive usage, and in the UI, Tinderbox's labelling of data types is case insensitive, i.e. 'number' or 'Number' are the same in meaning.
There are 14 types of attribute data types. Note that Action and Font types are not available for use by User 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 data type attributes and share a common default: an empty string. Boolean attributes default to false (which is not a string), Date attributes to the string "never", Interval attributes to the string "00:00" and Numbers to 0 (zero). Empty/Default values are discussed further for each action type in the articles linked in the list below.
A combined list of default values for each individual data type can be found here. See per-type listings for detail of the value sorting order of that type.
These are the current Tinderbox attribute data types