---
title: checkeventsource - X4 schema type
summary: checkeventsource: Controls diagnostics for a missing event-source object; its default is true. Changing a source variable alone does not restart the condition.
section: reference
kind: guide
status: reference
updated: 2026-10-27
tags: ["XSD","schema","types"]
sources: ["https://wiki.egosoft.com/X4%20Foundations%20Wiki/Modding%20Support/","https://www.w3.org/TR/xmlschema11-2/"]
---
## Meaning

checkeventsource: Controls diagnostics for a missing event-source object; its default is true. Changing a source variable alone does not restart the condition.

An XSD type constrains XML, rather than declaring a Lua return or the payload type of event.param. A valid schema value does not prove a successful game effect.

## Schema structure

`libraries/common.xsd`

| Property | Value |
| --- | --- |
| Construction | `restriction` |
| Base type | [`boolean`](wiki:schema-boolean-bf84d3d6) |

restriction narrows a base type; union accepts one of its branches; list describes whitespace-separated items. Enumeration values in one restriction are alternatives. Pattern syntax is XML Schema regex, not Lua patterns or JavaScript RegExp. Constraints inherited from the base type still apply.

## Example and result

```xml
<event_object_collided object="$Ship" check="false" />
```

**What happens:** check="false" suppresses this missing-source diagnostic. A later variable change does not automatically create a valid subscription.

Object and group variables must already exist in the correct MD / AI context. These are learning fragments, not a complete runnable mission.

## Used by

| Element | Attribute | Schema |
| --- | --- | --- |
| [`event_build_added`](wiki:api-mdevent-event-build-added-e177e0e5) | `check` | `libraries/common.xsd` |
| [`event_build_cancelled`](wiki:api-mdevent-event-build-cancelled-ab070aea) | `check` | `libraries/common.xsd` |
| [`event_build_finished`](wiki:api-mdevent-event-build-finished-7629377f) | `check` | `libraries/common.xsd` |
| [`event_character_animation_finished`](wiki:api-mdevent-event-character-animation-finished-8f6be6a0) | `check` | `libraries/common.xsd` |
| [`event_character_animation_started`](wiki:api-mdevent-event-character-animation-started-32dbc6a4) | `check` | `libraries/common.xsd` |
| [`event_long_range_scan_sent`](wiki:api-mdevent-event-long-range-scan-sent-e232eb0a) | `check` | `libraries/common.xsd` |
| [`event_object_changed_true_owner`](wiki:api-mdevent-event-object-changed-true-owner-d4bd10fc) | `check` | `libraries/common.xsd` |
| [`event_object_collided`](wiki:api-mdevent-event-object-collided-ea144cb6) | `check` | `libraries/common.xsd` |
| [`event_object_destroyed`](wiki:api-mdevent-event-object-destroyed-31ba2d1a) | `check` | `libraries/common.xsd` |
| [`event_object_dock_too_far`](wiki:api-mdevent-event-object-dock-too-far-5a6ff60d) | `check` | `libraries/common.xsd` |
| [`event_object_docked`](wiki:api-mdevent-event-object-docked-76ee1269) | `check` | `libraries/common.xsd` |
| [`event_object_docking_aborted`](wiki:api-mdevent-event-object-docking-aborted-97c4753f) | `check` | `libraries/common.xsd` |
| [`event_object_docking_denied`](wiki:api-mdevent-event-object-docking-denied-2f977468) | `check` | `libraries/common.xsd` |
| [`event_object_docking_impossible`](wiki:api-mdevent-event-object-docking-impossible-f9c10915) | `check` | `libraries/common.xsd` |
| [`event_object_docking_queued`](wiki:api-mdevent-event-object-docking-queued-034898e8) | `check` | `libraries/common.xsd` |
| [`event_object_order_cancelled`](wiki:api-mdevent-event-object-order-cancelled-de014228) | `check` | `libraries/common.xsd` |
| [`event_object_order_finished`](wiki:api-mdevent-event-object-order-finished-6bcd7797) | `check` | `libraries/common.xsd` |
| [`event_object_order_ready`](wiki:api-mdevent-event-object-order-ready-e783d19a) | `check` | `libraries/common.xsd` |
| [`event_object_signalled`](wiki:api-mdevent-event-object-signalled-5d5b1715) | `check` | `libraries/common.xsd` |
| [`event_object_undocked_from`](wiki:api-mdevent-event-object-undocked-from-a9b8b9e5) | `check` | `libraries/common.xsd` |
| [`event_object_undocking_started`](wiki:api-mdevent-event-object-undocking-started-887ea3ea) | `check` | `libraries/common.xsd` |
| [`event_weapon_fired`](wiki:api-mdevent-event-weapon-fired-36346bd2) | `check` | `libraries/common.xsd` |
| [`signal_objects`](wiki:api-md-signal-objects-053867ba) | `check` | `libraries/common.xsd` |


[All schema types](wiki:schema-types) · [Lua / MD value types](wiki:types)