---
title: "world-school-actors-world-event-play — Mova code model"
description: "Mova code model of world/src/school.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/world/src/school.rs.groupant/actors-world.groupant/event-play.groupant/"
---
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# world-school-actors-world-event-play

The groupant beside world/src/school.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.

## Facts

- **kind:** groupant_fragment
- **status:** partial source bound model
- **source:** [`world/src/school.rs`](https://github.com/ElamurAI/mova-free/blob/main/world/src/school.rs)
- **source SHA-256:** `06aaec6f562c2acc…`
- **covers:** Fold all initial holdings by actor. For each ordered event obtain (-1,0) for pay, else eff(verb) or return None. Quantity is e.n or (pre-event subject minus keep)*p/q. Update subject first; then explicit receiver, else first original holder different from subject if subject was not an original holder. Return the signed map without pruning. (bytes 57273–58414)
- **part of:** [world-school-actors-world](https://md.groupants.elamur.ai/free/en/mova/world/src/school.rs.groupant/actors-world.groupant/)
- **repository folder:** [`world/src/school.rs.groupant/actors-world.groupant/event-play.groupant`](https://github.com/ElamurAI/mova-free/tree/main/world/src/school.rs.groupant/actors-world.groupant/event-play.groupant)
- **repository commit:** `855da7bd4a7b`

> **Implementation material.** A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.

## Components

| component | label | where |
|---|---|---|
| **approximant** | partial source model | [forward](#forward) |
| **ast** | partial | `../../syntax.json` |
| **composition** | partial source model | [composition](#composition) |
| **cost** | partial source model | [cost](#cost) |
| **descriptant** | partial source model | [epoch-memory](#epoch-memory) |
| **invariant** | partial source model | [invariant](#invariant) |
| **tests** | partial source model | [checks](#checks) |

## Obernants

The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.

| id | type | label | where |
|---|---|---|---|
| `world-school-actors-world-event-play-behavior-complement` | behavior_complement | partial source model | [behavior-complement](#behavior-complement) |
| `world-school-actors-world-event-play-reverse-reconstruction` | reverse_reconstruction | partial source model | [reverse-reconstruction](#reverse-reconstruction) |
| `world-school-actors-world-event-play-fraction_time` | state_transition | partial source model | [fraction_time](#fraction-time) |
| `world-school-actors-world-event-play-transfer_conservation` | conservation_relation | partial source model | [transfer_conservation](#transfer-conservation) |
| `world-school-actors-world-event-play-receiver_selection` | order_relation | partial source model | [receiver_selection](#receiver-selection) |
| `world-school-actors-world-event-play-unknown_effect` | effect_boundary | partial source model | [unknown_effect](#unknown-effect) |

## Model text


Wave34, 2026-10-31. Source-bound helper model; no universal proof or approximation-error certificate. Historical parent epoch remains intact.

### forward

Fold all initial holdings by actor. For each ordered event obtain (-1,0) for pay, else eff(verb) or return None. Quantity is e.n or (pre-event subject minus keep)*p/q. Update subject first; then explicit receiver, else first original holder different from subject if subject was not an original holder. Return the signed map without pruning.

### invariant

All products, sums and differences must fit i64 and fractional q must be nonzero; truncating integer division is retained. Equal subject/receiver identities observe both updates. Unknown effect aborts the local result, not external callback side effects.

### cost

H holdings,J events,A actors: O((H+J)log A+JH) plus event/string clones, O(A) map. Callback cost additional.

### composition

Parent calls play before answer_of. Fractions inspect state after prior events but before this event; fallback receiver consults original holds, not the updated map. eff is supplied in native tests; dictionary/parser calls are omitted.

### behavior-complement

Exclude a successful result if a consulted non-pay effect is None; exclude final clamping of negative actors; exclude computing a fraction from the post-event balance. For supplied pure eff, no mutation of Reading holdings/events occurs.

### reverse-reconstruction

Given final map and a fixed event sequence/effects, compatible initial holdings are every ordered list whose aggregated counts replay to that map. Fractions, integer truncation, implicit receiver choice and duplicate holdings make this fiber many-to-one; retain intermediate maps and original-holder identities.

### fraction_time

Event j quantity depends on W_(j-1)[subject], so transferring three before all-but-two differs from computing both quantities at the initial ten.

### transfer_conservation

When both parties exist, are represented and a+b=0, the event preserves sum of actor balances, including identical actor identities; absent implicit receiver need not conserve.

### receiver_selection

Fallback selects the first eligible original holder; reordering original holds may change receiver despite identical initial aggregated map.

### unknown_effect

A pure callback returning None suppresses the entire Option map, although earlier local updates occurred. pay bypasses callback and uses the fixed debit. External callback effects would not be rolled back.

### checks

Exact world library selections: school::wave12_models::supplied_reading_transfer_and_fraction_use_prior_state. Current repeated debug/release outcomes and compiled controls are in the root sidecar wave34-evidence.md. Only these supplied-input tests are current evidence; older parent module-wide receipts are historical. Macro bodies remain opaque.

### epoch-memory

Prospective model saved before edits. This epoch deepens one existing node rather than renaming it. Production implementation unchanged; tests add helper-boundary observations where stated. No live lessons, frozen suites, model loading, teacher or network. Read-only symbolic relations are broader than the finite native domain.