(.xls). 3 stars: data is available in a non-proprietary structured format, such as Comma-separated values (.csv). 4 stars: data follows W3C standards, like using RDF and employing URIs. 5 stars: all of the other, plus links to other Linked Open Data sources. History The term "linked open data" has been in use since at least February 2007, when the "Linking Open Data" mailing list was created. The mailing list was initially hosted by the SIMILE project at the Massachusetts Institute of Technology. Linking Open Data community project The goal of the W3C Semantic Web Education and Outreach group's Linking Open Data community project is to extend the Web with a data commons by publishing various open datasets as RDF on the Web and by setting RDF links between data items from different data sources. In October 2007, datasets consisted of over two billion RDF triples, which were interlinked by over two million RDF links. By September 2011 this had grown to 31 billion RDF triples, interlinked by around 504 million RDF links. A detailed statistical breakdown was published in 2014. European Union projects There are a number of European Union projects involving linked data. These include the linked open data around the clock (LATC) project, the AKN4EU project for machine-readable legislative data, the PlanetData project, the DaPaaS (Data-and-Platform-as-a-Service) project, and the Linked Open Data 2 (LOD2) project. Data linking is one of the main goals of the EU Open Data Portal, which makes available thousands of datasets for anyone to reuse and link. Ontologies Ontologies are formal descriptions of data structures. Some of the better known ontologies are: FOAF – an ontology describing persons, their properties and relationships UMBEL – a lightweight reference structure of subject concept classes and their relationships derived from OpenCyc, which can act as binding classes to external data; also has links to 1.5 million named entities from DBpedia and YAGO Datasets DBpedia – a dataset containing extracted data from Wikipedia; it contains about 3.4 million concepts described by 1 billion triples, including abstracts in 11 different languages GeoNames – provides RDF descriptions of more than geographical features worldwide Wikidata – a collaboratively-created linked dataset that acts as central storage for the structured data of its Wikimedia Foundation sibling projects Global Research Identifier Database (GRID) – an international database of institutions engaged in academic research, with relationships. GRID models two types of relationships: a parent-child relationship