Hello all,

After several months of development and testing together with the WikiProject ShEx, Shape Expressions are about to be enabled on Wikidata.

First of all, what are Shape Expressions?

ShEx (Q29377880) is a concise, formal modeling and validation language for RDF structures. Shape Expressions can be used to define shapes within the RDF graph. In the case of Wikidata, this would be sets of properties, qualifiers and references that describe the domain being modeled.

See also:

• a short video about ShEx made by community members during the Wikimedia hackathon 2019
• introduction to ShEx
• more details about the language

What can it be used for?

On Wikidata, the main goal of Shape Expressions would be to describe what the basic structure of an item would be. For example, for a human, we probably want to have a date of birth, a place of birth, and many other important statements. But we would also like to make sure that if a statement with the property “children” exists, the value(s) of this property should be humans as well. Schemas will describe in detail what is expected in the structure of items, statements and values of these statements.

Once Schemas are created for various types of items, it is possible to test some existing items against the Schema, and highlight possible errors or lack of information. Subsets of the Wikidata graph can be tested to see whether or not they conform to a specific shape through the use of validation tools. Therefore, Schemas will be very useful to help the editors improving the data quality. We imagine this to be especially useful for wiki projects to more easily discuss and ensure the modeling of items in their domain. In the spirit of Wikidata not restricting the world, Shape Expressions are a tool to highlight, not prevent, errors.

On top of this, one could imagine other uses of Schemas in the future, for example building a tool that would suggest, when creating a new item, what would be the basic structure for this item, and helping adding statements or values. A bit like this existing tool, Cradle, that is currently not based on ShEx.

What is going to change on Wikidata?

• A new extension will be added to Wikidata: EntitySchema, defining the Schema namespace and its behavior as well as special pages related to it.
• A new entity type, EntitySchema, will be enabled to store Shape Expressions. Schemas will be identified with the letter E.
• The Schemas will have multilingual labels, descriptions and aliases (quite similar to the termbox on Items), and the schema text one can fill with a syntax called ShEx Compact Syntax (ShExC). You can see an example here.
• The external tool shex-simple is directly linked from the Schema pages in order to check entities of your choice against the schema.

When is this happening?

Schemas will be enabled on on test.wikidata.org on May 21st and on wikidata.org on May 28th. After this release, they will be integrated to the regular maintenance just like the rest of Wikidata’s features.

How can you help?

• Before the release, you can try to edit or create Shape Expressions on our test system
• If you find any issue or feature you’d like to have, feel free to create a new task on Phabricator with the tag shape-expressions
• Once Schemas are enabled, you can discuss about it on your favorite wikiprojects: for example, what types of items would you like to model?
• You can also get more information about how to create a Schema

See also:

• Main Phabricator board
• Technical documentation of the extension
• To enhance the interface, you can use this user script to highlight items and properties in the schema code and turn the IDs into links

If you have any questions, feel free to reach me. Cheers,