Known units

As of datamapper-api 1.6

You specify only the units, the domains are implied.

Units

Unspecified(Domain.Unspecified, 1),
    /** Time in seconds */
    Second(Domain.Time, 1), 
    /** Time in milliseconds */
    Millisecond(Domain.Time, 1e3f), 
    /** Time in microseconds */
    Microsecond(Domain.Time, 1e6f), 
    /** Time in nanoseconds */
    Nanosecond(Domain.Time, 1e9f),
    /** one absolute pixel position */
    AbsolutePixel(Domain.Position1D),
    /** Distance in metric meter */
    Meter(Domain.Distance),
    /** Distance in centimeters (tenth of a meter) */
    Centimeter(Domain.Distance, 10),
    /** Distance in millimeters */
    Millimeter(Domain.Distance, 100),
    /** Words containing natural language text. */
    Words(Domain.NaturalLanguageText),
    /** beats per minute (for music, or heart-rate) */
    BeatsPerMinute(Domain.Beats, 1),
    /** Amount of work in watts. */
    Watt(Domain.Work, 1),

Domains

public enum Domain {
    Unspecified, 
    Distance, 
    Time, 
    Position1D, 
    Position2D, 
    Position3D, 
    Temperature, 
    NaturalLanguageText, 
    Beats,
    Work
}