# Basic concepts

**LIBSAFE** is a preservation system based in the OAIS, ISO 14721:2012 standard. The following are basic concepts in the LIBSAFE implementation, as far as platform and system technical aspects are concerned.

**Object**: it is the basic preservation unit, and references what the application user wants to preserve for later retrieval. It is usually made up of a set of files, structured in folders, complying with some structure conditions, and accompanied by a set of metadata that allow for its cataloging and search in the system.

**Preservation**: action by which it is intended to guarantee the availability of all preserved objects over time, minimizing at the most any inaccessibility risks, regardless of the cause, that is, loss of the information, inability to access the data formats or data corruption.

**Ingestion:** process in which one or more objects are inserted in the preservation system, complying with certain criteria, and resulting in indefinite preservation in the system.

**Retrieval**: process by which a copy of the preserved object is obtained. The object will be retrieved according to the so called dissemination agreements, which consist of the conservation, transformation and evolution conditions of the original objects, depending on the access capacities assigned to them and the receiving public (designated community).

**Audit**: processes by which a preservation system checks the correct build of objects in the ingestion processes, through time in a periodic automatic or manual fashion, and in the retrieval processes, thus guaranteeing their conservation and availability.

**Preservation area**: a division of the repository that allows for the classification of the preserved objects with specific criteria that can be applied to the workflows, as for example,   audits, permissions and queries.

**Preservation plan**: set of conditions and controls configured in a unique way at a given moment, which guarantee the correct formation of the objects to be ingested into the system. This concept has an almost direct relation with the SIPs (Submission Information Package) and Delivery Agreement in the OAIS model.

**Metadata schema**: metadata set which are kept for a specific object, which allows for the cataloguing and search of the object.
