Mul language

For a substantial list of instances multiple languages typically have identical labels, aliases, and/or descriptions.

This impacts Wikidata storage, and the runtime performance of Wikidata Query, ListeriaBot, Pywikbot, and other Wikimedia Tools.

Technical impact

As a consequence Wikidata has storage issues, and Wikidata Query has performance problems with redundant labels, aliases and descriptions, taking up redundant storage, memory, and processing time. In addition to that, the item transaction history will grow much larger due to unnecessary duplication of labels.

Therefore in 2024 a new functionality was introduced: the mul labels and mul aliases. If a specific language does not have a label, the mul label is shown (without notice) instead. There is fewer emphasis on the English language. Therefore, as a principle, every item could have a mul label. The description should still be filled for each language, except when the description label would be the same for all instances of that type (e.g. firstname, lastname, category, etc.).

The item description for the mul language itself is never registered (because mul is not a real language).

Examples

• Names of persons, firstnames, lastnames → labels only to be stored for the mul language (no description); the same for aliases
• Descriptions of instances of firstnames, lastnames, categories, → should not be stored; to be retrieved at runtime from the instance language label
• Scolar articles and ISBN editions (the title should be only registered in the mul label, because a publication normally has only a single language). The actual language of the publication should be registered with (P407)

Impacted functions

• Item creation, item update
• Retrieval of labels (should take mul label as last resort)
• Pywikibot scripts
• Personal Babel registry (not required any more since January 2025; the mul language is automatically activated for everybody)
• Wikidata Query
• OpenRefine: register mul label via schema for persons, organisations, projects
• QuickStatements

Wikidata query

SELECT ?item ?itemLabel WHERE {
  SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],mul,en". }
  ?item wdt:P6104 wd:Q134895452.
}

Wikidata project documentation

• Only the mul-label is stored (Wikidata)
• Do not store obvious item descriptions (Phabricator)

Related problems

The same problem holds with inverse and derived statements.

• Inverse statements
• Derived statements (see Preferences → Gadgets → RelatedItems; M:1 statements should not be stored but retrieved from 1:M relationship)