Key Points

What is Wikidata?

Wikidata entities are known as Items, and each item is displayed on a page that is identified with the item’s “Q” number
Statements are assertions about items, which state relationships between items using wikidata properties.
Relationships between entities are known as Properties, and each property is identified with a “P” number
Statements are also known as “triples”
Wikidata and Wikipedia are complementary, but Wikidata is focused on basic claims or assertions, not descriptive or narrative information

Triples are the basic data structure of graph databases, and they are the conceptual structure of Wikidata statements.
Wikidata items are denoted by a human-readable label and a short description, and a unique identifier that begins with a Q. These items are the subjects of linked Wikidata statements.
Wikidata defines relationships between items, also known as triple predicates, with Wikidata properties.
Wikidata statements can capture library information, such as relationships like creatorship, publication, aboutness, and more.
Wikidata is part of a larger Linked Open Data ecosystem, and its data can be reused to build tools and services such as Scholia, InteractOA, and others.

Use the test instance of Wikidata (test.wikidata.org) to practice editing without affecting the live database.
New items require a label, description, and optional aliases; each item receives a unique Q-identifier.
Statements link properties (e.g. P569 “date of birth”) to values and should be supported by references pointing to reliable sources.
Identifiers such as VIAF, Library of Congress authority ID, IMDb ID, or ORCID connect a Wikidata item to external databases and increase its reliability.
Community norms govern how labels and descriptions are written; following them ensures consistency across Wikidata.
Wikidata distinguishes between a work and its editions — this is especially relevant for books and library materials.

Sourcemd and QuickStatements allow you to automatically add bibliographic metadata from DOIs or PMIDs to Wikidata.
The Author Disambiguator tool can help convert unstructured author strings to linked Wikidata items.
Tools for advanced editing are under active development and may change or be temporarily unavailable.

SPARQL is a query language for RDF data that allows you to search across the entire Wikidata knowledge graph.
The Wikidata Query Service at https://query.wikidata.org/ provides an interface to write and run SPARQL queries with auto-completion.
Results can be visualized in multiple ways including tables, maps, charts, and graphs using the Display menu or #defaultView.
It is good practice to modify existing example queries rather than writing queries from scratch.