Open data in the context of Open science

A data set (or dataset) is a collection of data. In the case of tabular data, a data set corresponds to one or more database tables, where every column of a table represents a particular variable, and each row corresponds to a given record of the data set in question. The data set lists values for each of the variables, such as for example height and weight of an object, for each member of the data set. Data sets can also consist of a collection of documents or files.

In the open data discipline, a data set is a unit used to measure the amount of information released in a public open data repository. The European data.europa.eu portal aggregates more than a million data sets.

Wikidata is a collaboratively edited multilingual knowledge graph hosted by the Wikimedia Foundation. It is a common source of open data that Wikimedia projects such as Wikipedia, and anyone else, are able to use under the CC0 public domain license. Wikidata is a wiki powered by the software MediaWiki, including its extension for semi-structured data, the Wikibase. As of early 2025, Wikidata had 1.65 billion item statements (semantic triples).

Open knowledge (or free knowledge) is knowledge that is free to use, reuse, and redistribute without legal, social, or technological restriction. Open knowledge organizations and activists have proposed principles and methodologies related to the production and distribution of knowledge in an open manner.

The concept is related to open source and the Open Definition, whose first versions bore the title "Open Knowledge Definition", is derived from the Open Source Definition.

data.gov.uk is a UK Government project to make available non-personal UK government data as open data. It was launched as closed beta in 30 September 2009; 16 years ago (2009-09-30), and publicly launched in January 2010; 16 years ago (2010-01). As of February 2015, it contained over 19,343 datasets, rising to over 40,000 in 2017, and more than 47,000 by 2023. data.gov.uk is listed in the Registry of Research Data Repositories re3data.org.

Open Government Data (OGD) Platform India or data.gov.in is a platform for supporting Open data initiative of Government of India. This portal is a single-point access to datasets, documents, services, tools and applications published by ministries, departments and organisations of the Government of India. It combines and expands the best features of India government's India.gov.in and the U.S. government's data.gov project.

Before data.europa.eu, the EU Open Data Portal was the point of access to public data published by the EU institutions, agencies and other bodies. On April 21, 2021 it was consolidated to the data.europa.eu portal, together with the European Data Portal: a similar initiative aimed at the EU Member States.

Public data can be used and reused for commercial or non‑commercial purposes. The portal was a key instrument of the EU open data strategy. By ensuring easy and free access to data, their innovative use and economic potential can be enhanced. The goal of the portal was also to make the institutions and other EU bodies more transparent and accountable.