As an editor, I want to refer to existing EntitySchemas in statementsnts on Items, Lexemes etc. in order to make it easier to find and classify themEnititySchemas. We need a new datatype to link to them fromEntitySchemas in statements.
**Example:**
Q5: correspondingHuman (Q5) is governed by the EntitySchema:E1234ma Human (E10).
We would like to link these via statements to show the link between the Item and the EntitySchema.
**BDD**
GIVEN an Item
AND an EntitySchema ca that govering the same topicns that class
THEN a new statement can be added that links the Item and the EntitySchema
**Acceptance criteria:**
[] a new datatype exists that allows linking to EntitySchemas
[] Only existing Entity Schemas can be selected as values
[] Link text should be the label of the eEntity sSchema
[] The value of that link should be exported in RDF as a URI (schema is to be decided by Engineers)
[] "What Links Here" on an EntitySchema instance should list all entities (Items, Lexemes etc.) linking to it through the new datatype
**Notes**:
* In the search field,* The value input of a statement should have the ability to use EntitySchema ID as well as the label of the EntitySchema. the schema ID is to be used (e.g.If the EntitySchema label is unable to be used in this instance the EntitySchema ID is acceptable.
* This property proposal has been approved and is awaiting this datatype: https://www.wikidata.org/wiki/Wikidata:Property_proposal/Shape_Expression_for_class
* Datatypes overview and definitions: https://doc.wikimedia.org/Wikibase/master/php/docs_topics_datatypes.html
* A checklist for introducing new datatypes used to exist at this link, no search by label etc)but no longer lives there: https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/Wikibase/+/refs/heads/master/docs/datatypes.wiki