---
title: assignmentexprlookup - X4 schema type
summary: assignmentexprlookup: X4 attribute schema type: base types, constraints and value alternatives.
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

assignmentexprlookup: X4 attribute schema type: base types, constraints and value alternatives.

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 | `union` |
| Union members | [`expression`](wiki:schema-expression-b8bc0e4f) |

Additional inline union branch:

| Property | Value |
| --- | --- |
| Construction | `restriction` |
| Base type | [`xs:string`](wiki:schema-xs-string-d5652e9b) |

| Constraint | Value |
| --- | --- |
| `enumeration` | `assignment.defence` |
| `enumeration` | `assignment.attack` |
| `enumeration` | `assignment.interception` |
| `enumeration` | `assignment.bombardment` |
| `enumeration` | `assignment.positiondefence` |
| `enumeration` | `assignment.assist` |
| `enumeration` | `assignment.mining` |
| `enumeration` | `assignment.trade` |
| `enumeration` | `assignment.build` |
| `enumeration` | `assignment.supplyfleet` |
| `enumeration` | `assignment.tradeforbuildstorage` |
| `enumeration` | `assignment.salvage` |
| `enumeration` | `assignment.prospect` |
| `enumeration` | `assignment.follow` |
| `enumeration` | `assignment.police` |
| `enumeration` | `assignment.watchdog` |

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

Use the attribute pages below for contextual examples. A generic executable example is not inferred from a type name alone.

## Used by

| Element | Attribute | Schema |
| --- | --- | --- |
| [`set_object_commander`](wiki:api-md-set-object-commander-f90a9d5e) | `assignment` | `libraries/common.xsd` |
| [`set_subordinate_group_assignment`](wiki:api-md-set-subordinate-group-assignment-70af38e5) | `assignment` | `libraries/common.xsd` |


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