The OAIS environment and information model, 496 words essay example
At the simple level, preservation requires that a digital object be kept safe and intact. Maintaining the integrity of a digital object as a sequence of bits overtime is a well understood process that can be carried out with little metadata. An identifier, a checksum or some other means of verifying the integrity of the object, dates of creation and maintenance, and an indication of who may access or act upon the object. The process of ensuring continued viability requires a rigorous system of backups, checks and crosschecks but once in place it is a mechanical operation based on a slim set of objective criteria. Maintaining reliable content that carries the key properties of an object forward over decades or centuries in a usable form, however is expected to require more than bit level preservation.
Renderability or the ability to open, play, display, execute, or otherwise access digital content is a far more difficult undertaking. Maintaining such usability requires compatibility between the form of the resource and an available hardware and software and environment. This may be achieved by changing the resource into a form that can be used in a contemporary environment or by maintaining or emulating the environment in which the resource can be use in the form in which it was achieved. Knowing the detailed specification of the objects format can enable the achieve to identify or if necessary write software to used it even if the programs with which it was originally used a long gone. Knowing the detailed specification of the environment where the object can be used help the achieved preserve or recreate such an environment in the future. In addition to the content files, information may be necessary to being multiple files into a usable object. A simple example is a book with images of pages and accompanying OCR text. Structural metadata can be used to express the relationship between components of a complex object and supports the user behaviors of viewing pages in sequence, jumping to earlier or later chapters. Structural metadata underlies audio, video and multimedia presentation as well. Like all metadata, structural metadata is also data that must be preserved if the object is to persist.
In order for a digital object to be useful in the future, it must not only be intact and playable. The content must also be meaningful where readability addresses the physical or syntactical form the object, understandability deals with the semantic integrity, or the meaning of the content. The Open Archival Information System (OAIS) model recognizes that this need can be met through both explicit representation information and implicit community knowledge. An achieve can decide to rely on community knowledge of German for example rather that decide to kept a German dictionary and grammar in addition to a German text. On the other hand, an achieved must retain a codebook for a social science data set, or else perfectly preserved and rendered columns and rows of number
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