A sentence is a value followed by a period.

A value is either:

• a complement
• a sequence
• a number
• a word

a word is a series of characters other than "'.:, or whitespace

a number is a decimal with optional leading sign, fractional part, and exponent

a sequence is any number of values each preceded by either , or ; (the delimiter must be consistent and may be surrounded on either side by whitespace, as seems appropriate)

a complement consists of:

• a prefixed value, called the head
• any number of values with the same prefix, called the "tail" (tails of more than one value are a shorthand for a sequence as the tail)

a prefixed value consists of:

• a "word", called the prefix
• a : (the "declension operator", which may not be surrounded by whitespace)
• a value