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Content Packaging

The OAIS Reference Model defines several types of information packages:

While the OAIS describes these packages in conceptual terms, it is necessary to select a suitable method for encoding in order to implement an OAIS compliant repository.

Below we consider several candidate "standards" which could provide the necessary packaging functionality: METS, CCSDS Packaging, MPEG DIDL and IMS Content Packaging.

  1. METS -Metadata Encoding and Transmission Standard

    The Metadata Encoding and Transmission Standard (METS) provides a framework of containers for packaging together descriptive, administrative, and structural metadata about digital objects and the complex links between them. It does so by providing an XML document format for encoding metadata necessary for both management of digital objects within a repository and exchange of such objects between repositories (or between repositories and their users). METS is being developed as an initiative of the Digital Library Federation (DLF) and is being maintained in the Network Development and MARC Standards Office of the Library of Congress.

    A METS document is made up of 4 sections: Descriptive Metadata, Administrative Metadata, File Groups and a Structural map. Metadata can either be included in the METS hub document or referenced via an identifier or locator.

  2. CCSDS Packaging

    The major advantage of this packaging format is that it is being developed by the CCSDS, so that it is being developed with OAIS in mind from the outset. It is also very much focused on scientific (largely space science) data and threfore readily caters for binary information.

  3. MPEG-21 DIDL (Digital Item Description Langauage)

    The second part of MPEG-21 (ISO/IEC 21000-2:2005) specifies a uniform and flexible abstraction and interoperable schema for declaring the structure and makeup of Digital Items. Digital Items are declared using the Digital Item Declaration Language (DIDL) and declaring a Digital Item involves specifying its resources, metadata and their interrelationships. Basically, a Digital Item is a combination of resources (such as videos, audio tracks, images etc), metadata (such as MPEG-7 descriptors) and structure (describing the relationship between resources).

    Within ISO/IEC 21000-2:2005 this Digital Item Declaration (DID) technology is described in three main sections:

    1. Model: The Digital Item Declaration Model describes a set of abstract terms and concepts to form a useful model for defining Digital Items.
    2. Representation: The Digital Item Declaration Language (DIDL) is based on the terms and concepts defined in the Model. It contains the normative description of the syntax and semantics of each of the DIDL elements represented in XML.
    3. Schema: The complete normative XML schema for DIDL comprising the entire grammar of the DID representation.

    The DID data model defines several entities including: Container, Item, Component, Anchor, Descriptor, Choice, Selection, Condition, Annotation, Assertion, Resource, Statement.

  4. IMS Content Packaging

    The IMS Global Learning Consortium develops and promotes open specifications for distributed, interoperable learning technologies for facilitating online distributed learning activities such as locating and using educational content, tracking learner progress, reporting learner performance, and exchanging student records between administrative systems. It is a non-profit organisation that includes members from the whole of the global eLearning community, including hardware and software vendors, educational institutions, publishers, government agencies, systems integrators as well as multimedia content providers. The Consortium provides a neutral forum in which members with competing business interests and different decision-making criteria collaborate to satisfy real-world requirements for interoperability and re-use.

    IMS specifications include: Content Packaging, Learning Resource Metadata, Question and Test, Enterprise, Metadata, Reusable Competencies Definition Information Model, Learner Information Package, Learning Design, Accessibility, Digital Repositories

    An IMS Content Package represents a unit of usable (and re-usable) content. This may be part of a course that has instructional relevance outside of a course organization and can be delivered independently, as an entire course or alternatively as a collection of courses. Once a Package arrives at its destination to a run time service, such as an LMS, the Package must allow itself to be aggregated or disaggregated into other Packages. A Package must be independent; that is, it must contain all the information necessary for use of the contents when it has been unpacked.