Trait IncidenceBase 

pub trait IncidenceBase: TopologyBase {
    type IncidenceId: TopologyId;
    type Role: Copy + Eq + Debug;
}

Incidence identity and role vocabulary for topology views with incidences.

Incidence support is separate from TopologyBase so graph-only views can expose nodes and edges without inventing endpoint identities or roles. Views that support relation-to-element participation records implement this trait.

Performance

Associated ID values should be compact O(1) handles. Role describes how an element participates in a relation. Arbitrary incidence payloads should be exposed by separate traits keyed by Self::IncidenceId.

Required Associated Types

type IncidenceId: TopologyId

Identity of one element’s participation in one relation.

Performance

Values should be O(1) to copy, compare, order, hash, and debug-format.

type Role: Copy + Eq + Debug

Implementation-defined participation role.

A role is a topology-level label for an incidence. Rich metadata can be attached by separate payload traits or storage layers keyed by Self::IncidenceId, [Self::RelationId], or [Self::ElementId].

The Copy + Eq + Debug bound lets role-aware generic algorithms compare, copy, and debug-format roles without each consumer restating the bound; the role’s meaning stays implementation-defined.

Performance

perf: unspecified. Implementations should prefer structural role values or compact role handles; rich metadata should be reached through separate payload access traits.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors