Glossary of terms




A colloquial term for a large group of servers managed by one or more organizations known as "cloud providers": customers of the cloud provider can purchase the use of servers and other hosted services and run their own software, all by connecting to the cloud provider over the internet. In turn, their own customers access and use their software over the internet.

Example: Amazon Web Services (AWS) is a cloud provider. Company "Ex", who for the purposes of our example makes an online spreadsheet application called "ExampleCalc", rents servers from AWS, hosts their software on some of AWS's cloud servers and makes access to ExampleCalc available to their own customers. Ex's ExampleCalc is now a cloud-hosted application on AWS.



A piece of software that stores organized information and makes it available to other applications, often by means of a set of commands called a query language. "Database" is often used instead of the more formal name, DBMS. "Database" can also refer to the data itself that such an application stores. Most people don't use "DBMS" when referring to the type of application, instead using the word "database" to refer to both and relying on context to distinguish them.

Data object


An individual piece of data that's being processed by a computer. It may be a single value or a group of values, and it may have a label or "identifier" with which one can refer to it. A data object has a data type.

Data type


The nature of a piece of data (a numeric value, string, URL, timestamp, etc.) and the specific form that it takes.

Examples: integer (4); string ("Mary had a little lamb"); URL (""); time (Thu 1 Jan 01:00:00 EST 1970).



DataBase Management System — Database management system. The formal name for a "database" when that term is used to refer to a piece of software that manages stored data, and not the data store itself.



A piece of software that allows users to perform full-text searches across large bodies of data. Elasticsearch is often used in conjunction with Wikibase to augment MediaWiki’s own search.



(MediaWiki) A piece of software that extends MediaWiki's default functionality, that which MediaWiki can do by default. A good example is the VisualEditor, which allows users to edit wiki entries as if they were using a word processor.



In RDF, an object, concept, or event that appears in a triple (the subject, possibly also the object).

Examples: "red", "empathy", "New Year's Eve"

See Wikidata's own glossary entry on 'item'.



(noun) Synonym for server.

(verb) To host software means to install it on a server and, typically, to then offer access to that software over the internet.

Linked Open Data


Linked Open Data (LOD) — Data that is structured, public and interlinked with other data across the internet. As Sir Tim Berners-Lee describes it: "Linked Open Data is linked data which is released under an open license, which does not impede its reuse for free."

See the excellent Wikipedia article on the topic and this helpful description of five-star data.



A piece of software running in a web server that lets you create and edit wikis. MediaWiki is free software developed by the MediaWiki community and distributed under the GNU Public License, GPL.



In the query service, prefixes define which Wikibase instance a query element refers to. Although Wikidata is the default, queries can define different prefixes as well.


PREFIX exd: <>
PREFIX exdt: <>
    ?item exdt:P5 exd:Q146 .
    ?item exdt:P27 ?creationDate .

meaning that:

  • prefixes exd and exdt identify the aliases of corresponding URLs
  • following both triplets <subject> <predicate> <object> allow to select (generally in a loop):
  • the items of current store having property P5 with value Q146. P5 is defined in the external store exdt, and the value is defined in store exd. Save the value of the element in variable item
  • among these elements select those having a property P27 and assign the value to variable creationDate

Thus we get a list of couples (element, creation date) where property P5 is Q146 for all.



In RDF, a descriptor that appears in a triple (the predicate) that describes the relationship between two pieces of information.

Examples: "is capital of", "inventor of", "instance of"

See Wikidata's own glossary entry on 'property'.



A command used to request information from a database.

Query language


A system of commands used to request information from databases.
Structured Query Language — SQL is a common example of a query language; numerous other query languages have based many of their commands and syntax on SQL. Example: SPARQL. These are "languages" in the sense of programming languages or markup language.

Query service





Relational DataBase Management System — See DBMS. A relational database stores its data in tables and other structures, according to a system or plan known as a schema. All databases that can be used to run MediaWiki are relational: MySQL, PostgreSQL, SQLite, etc.

A relational database exists in contrast to a non-relational or NoSQL database, where data is stored unstructured in collections.

Resource Description Framework — A system of representing information in a structured way, used by Wikibase and other software in the Linked Open Data web.

See the W3C's document on RDF concepts.



The system of organization that a relational database uses to store its data. Among other structures, a schema contains tables, views and indices.



A computer on which pieces of software run for long periods of time, such as databases. Also: the software that runs on such computers, such as a web server. The senses are often used interchangeably; whether the speaker is referring to the computer itself or the software running on the computer can be difficult to determine and depends on context.



SPARQL Protocol And RDF Query Language — A query language used to interact with data in RDF data stores such as Wikibase.

See the Apache Software Foundation's SPARQL tutorial.



In RDF, data is presented in the following form: a subject (item), a predicate (property) and an object (item, quantity, mathematical expression...).

  • Example: "<Berlin> <is the capital of> <Germany>."
  • Example: "<Berlin> <has a population of> <3.7 million>."

These three pieces of information together are called a triple, and as a single piece of information it's called a statement.

See the Wikidata glossary entry, the Wikipedia article on triples and the W3C's primer.

Structured data


Information that's been highly organized so that it can be easily processed by computers.



See Statement.



WikiData Query Service — Software that provides a way to extract data from Wikibase by using the SPARQL query language.

See Wikidata's query service doc.

Web server


A piece of software that serves web pages and content. Sometimes that content is generated by other server software, which is said to be running "in" the web server.

More precisely, a web server is an application that receives requests and answers them by sending back data that a web browser (Mozilla Firefox, Google Chrome, etc.) uses to display a web page to an end user. A web server communicates using the HTTP protocol and serves information over the internet.



A knowledge base, often public, where anyone with access can add and edit information. "Anyone with access" might mean everyone in an organization or everyone in the world.



Wikibase is free software that stores and organizes information that can be collaboratively edited and allows it to be easily consumed by computers, translated into multiple languages and shared with the rest of the world as part of the Linked Open Data web. It is an extension for MediaWiki.