Library The ACM Portal is an online service of the ACM. Its core are two main sections: ACM Digital Library and the ACM Guide to Computing Literature. The ACM Digital Library is the full-text collection of all articles published by the ACM in its articles, magazines and conference proceedings. The Guide is a bibliography in computing with over one million entries. The ACM Digital Library contains a comprehensive archive starting in the 1950s of the organization's journals, magazines, newsletters and conference proceedings. Online services include a forum called Ubiquity and Tech News digest. There is an extensive underlying bibliographic database containing key works of all genres from all major publishers of computing literature. This secondary database is a rich discovery service known as The ACM Guide to Computing Literature. ACM adopted a hybrid Open Access (OA) publishing model in 2013. Authors who do not choose to pay the OA fee must grant ACM publishing rights by either a copyright transfer agreement or a publishing license agreement. ACM was a "green" publisher before the term was invented. Authors may post documents on their own websites and in their institutional repositories with a link back to the ACM Digital Library's permanently maintained Version of Record. All metadata in the Digital Library is open to the world, including abstracts, linked references and citing works, citation and usage statistics, as well as all functionality and services. Other than the free articles, the full-texts are accessed by subscription. There is also a mounting challenge to the ACM's publication practices coming from the open access movement. Some authors see a subscription business model as less relevant and publish on their home pages or on unreviewed sites like arXiv. Other organizations have sprung up which do their peer review entirely free and online, such as Journal of Artificial Intelligence Research, Journal of Machine Learning Research and the Journal of Research and Practice in Information Technology. ACM has made its publications from 1951 to 2000 open access through its digital library on 7 April 2022 as part of its 75th anniversary of the organisation. Membership grades In addition to student and regular members, ACM has several advanced membership grades to recognize those with multiple years of membership and "demonstrated performance that sets them apart from their peers". The number of Fellows, Distinguished Members, and Senior Members cannot exceed 1%, 10%, and 25% of the total number of professional