Struct TopDownFairModel

pub struct TopDownFairModel;

The TopDownFair model evaluates candidates based on the aggregate support they receive from external backers.

Concept: Aggregated External Fairness

Each candidate has a list of (Backer, Backed) pairs representing individual endorsements. The model sums these contributions using saturating addition to prevent overflow and sorts candidates in descending order by their total received backing.

Characteristics:

• Fair aggregation: Each candidate’s score is the sum of their backers’ support.
• No self-weighting: Excludes self-stake to prevent dominance by self-funding.
• Overflow-safe: Uses Saturating arithmetic to avoid overflow errors.
• Context-free: Deterministic and stateless ranking.

Applications:

• Governance elections prioritizing external community support
• Fair staking models with anti-self-dealing constraints
• Collaborative credit or delegation-based systems

Example:

let input = vec![
    ("Alice", vec![("Bob", 10), ("Carol", 20)]),
    ("Dave", vec![("Eve", 15), ("Frank", 15)]),
    ("Grace", vec![("Heidi", 5), ("Ivan", 10)]),
];
let output = TopDownFair::compute(input, None);
// Aggregated totals:
// Alice: 30, Dave: 30, Grace: 15
assert_eq!(output, vec!["Alice", "Dave", "Grace"]);

Reference:

• Weighted voting - Wikipedia
• Delegated voting / Liquid democracy
• Osborne, M. J., An Introduction to Game Theory, Oxford University Press, 2004 (proportional influence)

Trait Implementations

impl Debug for TopDownFairModel

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for TopDownFairModel

fn default() -> TopDownFairModel

Returns the “default value” for a type.

impl<Candidate, FairWeight, Backer, Backed, Input, Output> PurePluginModel<Input, (), Output> for TopDownFairModel

where Input: FromIterator<(Candidate, FairWeight)> + IntoIterator<Item = (Candidate, FairWeight)> + Clone, Output: FromIterator<Candidate>, FairWeight: FromIterator<(Backer, Backed)> + IntoIterator<Item = (Backer, Backed)> + Clone, Backed: Clone + Ord + Zero + Saturating, Candidate: Clone,

fn compute(&self, input: Input, _context: &()) -> Output

Computes the fair aggregated rank of candidates imperatively.

• Iterates over each candidate and sums their backers’ contributions using saturating addition.
• Sorts candidates by descending total backing.
• Returns only the ordered list of candidates.