level:
level
single
multiple
any
count: pattern
count
from: pattern
from
format: string like Java 1.1's DecimalFormat class
format
DecimalFormat
letter-value:
letter-value
alphabetic
traditional
grouping-separator: char
grouping-separator
grouping-size: number
grouping-size
lang:
lang
en
fr
fr-CA
ch
etc.