OpenTally/docs/blt.md

# BLT file format

OpenTally accepts ballot data in the BLT file format, as described by [Hill, Wichmann & Woodall](https://www.dia.govt.nz/diawebsite.NSF/Files/meekm/%24file/meekm.pdf) for their implementation of Meek STV. The BLT file format is also used by [OpenSTV/OpaVote](https://www.opavote.com/help/overview#blt-file-format), Lundell's [Droop](https://github.com/jklundell/droop/wiki/BltFileFormat) and Otten's [eSTV](https://web.archive.org/web/20020606014623/http://estv.otten.co.uk/) (where it is known as a DAT data transfer file).

The file format is as follows:

```
4 2
-2
3 1 3 4 0
4 1 3 2 0
2 4 1 3 0
1 2 0
2 2 4 3 1 0
1 3 4 2 0
0
"Adam"
"Basil"
"Charlotte"
"Donald"
"Title"
```

The first line (`4 2`) indicates that there are 4 candidates for 2 vacancies.

The second line (`-2`), which is optional, indicates that the 2nd candidate (Basil) has withdrawn. Multiple withdrawn candidates may be specified on this line, e.g. `-2 -3 -4`.

The third line (second, if there are no withdrawn candidates) begins the ballot data. `3 1 3 4 0` indicates that there were 3 ballots which voted, in order of preference, for the 1st candidate (Adam), then the 3rd candidate (Charlotte), then the 4th candidate (Donald). A `0` optionally indicates the end of the list of preferences.

The end of the list of ballots must be indicated with a single `0`.

The next lines give the names of the candidates, up to the number of candidates specified on the first line (in this case, 4). Each candidate's name, unless a single word, must be surrounded by quotation marks.

The final line gives the name of the election, which, unless a single word, must be surrounded by quotation marks.

Newlines are optional, but if not provided, the `0` at the end of each ballot's preferences is mandatory.