Core of Zodiac

All structures in these documents, unless otherwise mentioned, are sub-types of a single structure, named zodiac:zodiac. This structure has the form

zodiac:zodiac (origin start finish)

where origin is an zodiac:origin struct, while start and finish are zodiac:location structs. The origin field is currently unused, and the zodiac:origin struct is correspondingly unspecified. Locations are represented as a tuple of the line number, column number, file offset and file name:

zodiac:location (line column offset file)

The line and column fields contain positive integers starting at 1, while offset contains a non-negative integer that starts at 0. The type of file is left unspecified. The zodiac:period struct provides the location of periods in improper lists:

zodiac:period (location)

Note that zodiac:origin, zodiac:location and zodiac:period are not sub-types of zodiac:zodiac.