Dear all, I thank you for your efforts. I have seen with a lot of interest the report of Dr. David Abián about property constraints for Wikidata as shown at https://www.wikidata.org/wiki/Wikidata:2020_report_on_Property_constraints. The report provides a significant overview of the usefulness and current status of Wikidata property constraints to ameliorate the consistency of the Wikidata ontology. However, I think that property constraints suffer from critical limitations that currently harm the quality of linked data of Wikidata. That is why I propose a roadmap for adding support of ontological reasoning to Wikidata. This proposal is inspired from the works about the use of ShEx for ontology validation of Wikidata and from a work we sent for review to World Wide Web Journal:

1. Link Shape Expressions to corresponding Wikidata classes and use them to validate the use of properties in Wikidata. This is possible through the acceptance of https://www.wikidata.org/wiki/Wikidata:Property_proposal/Shape_Expression_fo.... 2. Infer Shape Expressions for all major Wikidata classes. This is possible using https://wikitech.wikimedia.org/wiki/Tool:Wikidata_Shape_Expressions_Inferenc.... 3. Verify Shape Expressions for all Wikidata classes by hand 4. Propose two new Wikidata properties: Valid Subject Class and Valid Object Class. These two properties will be used to define the accurate classes for the subject and object of a Wikidata property. For example, The subject of a “Drug used for treatment” relation should be a disease or a symptom and its object should be a drug or a chemical substance. 5. Define practical guidelines of adding Inverse property (P1696) statements. This property links between a property and its inverse. For example, “Drug used for treatment” and “Medical condition treated” are two inverse properties. Where the relation is symmetric, the inverse of a given property is the same property. For example, “Significant drug interaction” is the inverse property of “Significant drug interaction” 6. Add Valid Subject Classes and Valid Object Classes for all Wikidata properties when applicable. Wikidata Query Service can be used to automate the process. This is shown in the paper that was sent for review to World Wide Web Journal. 7. Add Inverse properties to each Wikidata properties. “Valid Subject Class” and “Valid Object Class” are used as constraints for Inverse property statements. In fact, a property can have more than one inverse property and each inverse property is used according to context. Wikidata Query Service can be used to automate the process. This is shown in the paper that was sent for review to World Wide Web Journal. 8. Develop a tool that combines statements between WIkidata properties and Shape Expressions of Wikidata properties to validate the use of Wikidata property and identify deficient statements. I ask about what you think about this detailed roadmap. I am currently convinced that this method will help us solve the linked data quality matter for Wikidata. I can help in applying this roadmap. Please reply me soon. Yours Sincerely, Houcemeddine Turki