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Glossary of OpenTally terminology
Terminology relating to the single transferable vote is varied and not standardised. This page describes how terms are used in OpenTally.
Candidates
A continuing candidate is a candidate who has been neither elected nor excluded (nor doomed, when constraints are in use). Other sources sometimes call this a hopeful candidate.
A candidate is elected upon meeting the quota. A candidate is excluded upon being eliminated from the count.
When constraints are in use, a candidate is guarded if they must be elected to obtain a result conforming to the constraints, and doomed if they must not be elected to obtain a result conforming to the constraints.
Stages
In the single transferable vote, counting proceeds in stages. In OpenTally, the defining feature of a stage is that it is at the end of each stage that candidates are declared elected or excluded. Other sources sometimes call these rounds or counts.
The first stage of an election count is the distribution of first preferences. Each subsequent stage involves the distribution of an elected candidate's surplus, or the exclusion of a candidate.
According to the particular rules in use, the exclusion of a candidate may take place over multiple stages. Other sources sometimes call these substages, but where candidates are declared elected or excluded at the end of each, OpenTally still calls these stages.
Ballots and votes
A ballot represents a sequence of preferences, and when allocated to a particular candidate, has an associated value. The unit for value is the vote. The initial value associated with a ballot at the distribution of first preferences is the ballot's weight.
A parcel is a set of ballots allocated to a particular candidate (or exhausted) all at the same value (relative to their weight). Other sources sometimes call this a bundle or batch.
In OpenTally, value is tracked at the level of parcels rather than individual ballots, so the value of an individual ballot is calculated when required as the ballot's weight multiplied by the value of the parcel containing it.
A candidate's progress total is the total value of all ballots allocated to that candidate.
Transferring ballots
The next available preference on a ballot is the continuing candidate who appears highest on the ballot's preferences. During a surplus distribution or exclusion, a ballot is said to be transferable if there is a next available preference. If not, the ballot is said to be non-transferable and set aside as exhausted.
Some sources differentiate between ballots which are formal (valid) and informal (blank or invalid for some reason or another). OpenTally assumes that all ballots are valid. The number of blank ballots is reported as the number of ballots exhausted in the first stage.
A candidate has a surplus when their progress total exceeds the quota. During a surplus distribution, the surplus is divided by the number of ballots or votes examined in the distribution (according to the particular rules in use), and the quotient is called the surplus fraction. Other sources, particularly those using the exclusive Gregory or unweighted inclusive Gregory methods, often call this the transfer value.
If, as a result of rounding, the number of votes transferred during a surplus distribution is less than the surplus, the difference is called loss by fraction. Other sources sometimes call this lost fractions, vote fractions not transferred due to rounding, or similar. Some other sources consider the exhausted votes and loss by fraction together, and call the total the non-transferable difference, votes lost, or similar.