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1USER - One-user perpetual license. A title purchased as 1USER means that one (1) user can access the document. 

3USER – Three-user perpetual license. A title purchased as 3USER means three (3) users can access the document concurrently. Users will be automatically rolled over to the next available copy if the first one or two are in use.

ATO - Access-to-own. This model is an unique usage-based acquisition model for eBooks, where all spend contributes towards ownership, thus allowing customers to control budget while potentially providing access to a wider pool of titles.

Book – A document available on Ebook Central. Interchangeably called book, document, or title. Most Ebook Central titles are books, but some are journals, maps, or sections of books made available as a separate document by the publisher.

Channel – Also referred to as a site. A hosted Ebook Central website that provides access to all the documents (subscription, perpetual access, or DDA) for a particular customer such as a school, company, university, or public library.

Collection - An aggregate of books sharing one or more similar attributes.

DDA - Demand Driven Acquisition, which represents Ebook Central's on-demand collection.

DOC ID - Document Identifier. Each publication (title/ book) is defined by a document identifier, which is visible on its description.

Extended Access - Also referred to as Turnaway Prevention, allows an administrator to set rules for a sought-after, but in-use, single-user title to initiate a just-in-time loan, upgrade, or additional purchase – thereby extending availability on demand.

Loan - Also referred to as Short-Term Loan or STL. A loan is an Ebook Central book that is made available on an Ebook Central site for 1, 7, 14 and 28 days (depending on the library’s preferences) at a fraction of the book's purchase price.

NL - Non-Linear access. Under this model, titles are not restricted to linear distribution - one patron at a time - but rather they can be lent to any number of patrons concurrently. The number of days used for each loan instance is subtracted from the total number of annual loan days set for the title - usually 325.

Perpetual Access – Purchased titles. If an Ebook Central site purchases titles, they have access to them as long as they have access to their Ebook Central site. Even if a publisher decides to remove a title from Ebook Central, if an Ebook Central site has purchased the title it will not be removed. Perpetual access titles can be purchased as either single-user-only (1USER), three-user (3USER), non-linear (NL), or unlimited access (UA). Please note that not all titles are available in every access model.

Site – An Ebook Central site (also called a “channel”) is a hosted Ebook Central website that provides access to all the documents (subscription, perpetual access and DDA) for a particular customer such as a school, company, university, or public library.

SITE ID - Site Identifier. Each channel is assigned a site identifier, which defines it.

STL – Short-Term Loan. A loan is an Ebook Central book that is made available on an Ebook Central site for the required number of days (depending on the library’s preferences) at a fraction of the book's purchase price.

Subscription collection – A set of documents that are essentially leased to an Ebook Central site, typically on an annual basis. The specific documents in subscription collections can change without prior notice, but the expectation is that we will add more than we remove. The MARC Updates tab announces changes as possible. MARC record adds and deletes reflect all additions to and removals from your subscription collections. If an Ebook Central site requires guaranteed access to a particular document (i.e., it is being assigned for a class), the library should purchase it because with subscription collections, there is no guarantee that the title won’t be removed.

Title – Often used to mean an Ebook Central document; interchangeably called book, document, or title. Most Ebook Central documents are actual books, but some are journals, maps, or sections of books made available as a separate document by the publisher.

Triggerable use – The amount and type of use required for a DDA or STL+DDA document to be triggered for purchase or loan.

Turnaway - When a user tries to open an Ebook Central document but it is a single-user book (or the last copy of a 3USER book) that's already in use, they receive the alert.

Turnaway Prevention - also referred to as Extended Access, allows an administrator to set rules for a sought-after, but in-use, single-user title to initiate a just-in-time loan, upgrade, or additional purchase – thereby extending availability on demand. 

UA - Unlimited Access - Unlimited access titles can be accessed by an unlimited number of users at the same time. All titles in subscription collections (for example, Academic Complete) are unlimited access titles.