Wikidata:WikiProject Ontology/Cleaning Task Force

This page serves as the main page for the ontology cleaning task force's efforts to clean up the Wikidata ontology.

The task force arose from a presentation (https://commons.wikimedia.org/wiki/File:Wikidata_Challenges_in_Semantic_Web_Community.pdf) by Andrea Westerinen at the 2023 Wikidata Data Quality Days (https://www.wikidata.org/wiki/Wikidata:Events/Data_Modelling_Days_2023)

Anyone interested in working to improve the Wikidata ontology is welcome to join the task force.

Scope

Just about any effort to improve the Wikidata ontology is considered in scope, ranging from theoretical analyses of the ontology, to techniques for reasoning in Wikidata, to implementation of tools that help improve the ontology, to documentation of problems with the ontology, to direct editing of the ontology. There is a welcome page that gives some background on the Wikidata ontology and the task force.

Areas of Interest

The task force has investigated several areas of the Wikidata ontology. Here are some of them and their current status:

Disjointness: Ege and Peter looked at disjointness violations and made some changes that had very large effects. See Disjointness for more information.
Class Order: Peter and Ege looked at class order and found a lot of problems. Peter is currently looking at class order problems triggered by an item being both an instance and a subclass of the same class. See Class Order for more information.
Verb senses: A group has been figuring out how to best include more information about verb senses in Wikidata.
Books: Kalliopi and Ege have been looking at the representation of books.
Libraries: There have been comments on problems representing libraries. The task force may look at these problems, potentially in a broader sense.

If you are interested in anything related to cleaning the Wikidata ontology, feel free to add your interest above.

Meetings

The task force uses Google Meet for meetings, as described in the task force's calendar. Currently meetings are Tuesday at 11:30 am ET (currently UTC-4). Members of the task force are active in the Wikiproject Ontology telegram group.

Next meeting agenda

Interested parties should add agenda items for topics they wish to discuss. The default agenda has places for questions about the Wikidata ontology and reports on the current efforts. If there is significant work on any effort please add something to the agenda.

Tuesday, 18 August 2026, 11:30 EDT (UTC-4)

Our meeting length is limited to 60 minutes by Google so meetings may be terminated abruptly.

Welcome new members
- If you can't make meetings please add information to this page about your interests and activities.

Data Organization and Quality User Group
- Almost ready for next publicity step
- See https://meta.wikimedia.org/wiki/User:Peter_F._Patel-Schneider/Data_Organization_and_Quality

Best Practices for Metaclasses
- Peter created https://www.wikidata.org/wiki/Wikidata:WikiProject_Ontology/Metaclasses
- Anything new?

Other topics

Tuesday, 25 August 2026, 11:30 EDT (UTC-4)

zelph: from culprits to fixes (Stefan) — please budget at least 30 minutes
- A different format from the two previous sessions: slides rather than a live terminal session, with two short live checks as evidence. One claim, not a feature tour. Feedback after the last two sessions was that the live-demo format made it hard to follow.
- Starting point is section 4.3 of Doğan & Patel-Schneider, Disjointness Violations in Wikidata: finding the culprits is a query, but identifying the mistake behind a culprit is explicitly out of scope there and done by hand. Section 7 asks for a tool that shows culprits in context and "pointed out changes that would eliminate the issue". That step — not query speed — is what I would like to discuss.
- Concretely: ranking candidate subclass of (P279) removals by how many of the 14,480 culprits each one eliminates, the way the single fix on gene (Q7187) accounted for 10,656 of them. Whether this is worth building is exactly what I want the group's opinion on before I build it.
- What I am asking for: which error classes are worth a regularly regenerated report, and what such a report has to contain to be usable by an editor.
- No neural-network material this time — that would be a separate session if there is interest.

Previous meeting notes

See Wikidata:WikiProject Ontology/Cleaning Task Force/Meetings for notes from prior meetings.

Participation

Anyone interested in working to improve the Wikidata ontology is welcome. Add your user identification below to join the group. Add issues that you are interested in or currently work on to the sections below.

Current and Past Participants

Wikidata Ontology Course

Peter and Ege ran a course on the Wikidata Ontology in May and June 2025.

The second offering of the course will be given in May and June 2026. For more information see the course page, above.

Current efforts and Information

See the Activities Page for information on some activities that have been done within the task force.

Related Information

There is a page on what might be done to improve the Wikidata ontology at https://www.wikidata.org/wiki/Wikidata:Ontology_issues_prioritization. This was a result of a survey of Wikidata users on what problems they encountered when using the Wikidata ontology.

https://www.wikidata.org/wiki/Wikidata:Tools/Enhance_user_interface#Classification.js is a useful tool to show parts of the Wikidata ontology.