Trait OccupiesBusinessKey 

pub trait OccupiesBusinessKey {
    // Required method
    fn occupies_business_key(&self) -> bool;
}

Whether a process in this state still occupies its business key.

MaKo processes are correlated by a business key — usually the MaLo — through the process registry’s correlation index. That index is append-only: an entry is written when a process spawns and nothing removes it when the process finishes. So “is there an entry for this MaLo?” cannot answer “is a process still running for this MaLo?” — only the replayed state can.

A duplicate guard that refuses on entry presence therefore blocks a business key permanently. That is wrong for every MaKo process family: an Anmeldung the NB rejected is finished, and the corrected Anmeldung that follows is a normal flow, not a retry.

Implement this on a workflow’s Workflow::State so the decision sits next to the state definition. Write the impl as an exhaustive match rather than a catch-all, so adding a state variant forces a deliberate choice instead of silently inheriting whichever default the catch-all happened to pick.

Required Methods

fn occupies_business_key(&self) -> bool

true while a new process for the same business key must be refused.

Return false for the pre-start state and for every terminal state (completed, rejected, timed out). When a state’s meaning is genuinely ambiguous, return true: refusing a legitimate process surfaces as a 409 the operator can see, whereas admitting a duplicate one puts a second live process on the same MaLo, which the market cannot untangle.

Dyn Compatibility

This trait is dyn compatible.

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

Implementors