Open science refers to collaborative networks which share resources and ideas, and aims to facilitate the generation and dissemination of scientific results. Disclosing research data (Open Data), software source codes (Open Source) and making publications freely accessible (Open Access) are thus parts of the Open Science movement.

The 2002 Budapest Open Access Initiative (BOAI) defines OA as making content both free to read and free to reuse. Some definitions are less strict and consider as OA the research literature free to read online.

From these definitions, many different types of OA have coevolved. It is therefore important to consider OA as a spectrum of different economic models, whose diversity tends to complicate the current societal discussions about OA.

Different models of OA

Two main types prevail in the OA world: The Gold and Green OA (see diagram below).

In the Gold OA, the publication is made freely available by publishers, either from Day 1 (Direct OA) of after a period called embargo (Delayed OA). Some subscription-based journals also offer the option to make publications freely available in exchange of an article processing charge (APC) paid by the author or the author’s institution. This model of Gold OA is called Hybrid OA. The DOAJ, Directory of Open Access Journals, provides a complete and updated list of all OA journals, with or without APC.

The Green OA means that the authors self-archive their work, in addition to publishing it in a toll-access journal. A copy of the preprint (i.e. work published before peer-reviewing), manuscript or published paper is uploaded either into a personal website, or an institutional or subject-based online archive called repository, such as arXiv for Physics or PubMedCentral for medicine and life sciences.