PREMIS Data Dictionary, Version 3.0, now available
The PREMIS Editorial Committee is pleased to announce the availability of PREMIS Data Dictionary for Preservation Metadata, Version 3.0. This is a major new version with a revised data model, enhancing the ability to express information about software and hardware environments and intellectual entities.
Specific changes in this version include:
- Make Intellectual Entity another category of PREMIS Object. In versions 1 and 2 an Intellectual Entity was a separate entity and was out of scope for description using PREMIS except for an identifier to link to it from other PREMIS entities. This change will enable a repository to represent an aggregate, such as a collection, FRBR work or expression, fonds or series, in order to capture descriptive metadata, to associate business requirements with it (such as significant characteristics, risk definitions, guidelines for preservation actions, etc.), to support structural and derivative relationships, to make rights statements, and to establish relationships to preservation events. In addition it will allow for the repository to capture versioning information and metadata update events at the Intellectual Entity level for resources such as articles or issues.
- Revise the data model so that software and hardware environments can be described and preserved reusing the Object entity. In order to preserve Digital Objects, repositories need to have information about the elements of the technical stack of software, hardware and other dependencies needed to correctly interpret the representations, files and bitstreams. This is particularly important for certain types of resources that are dependent on combinations of hardware and software for their use, e.g. multimedia or web sites. In previous PREMIS versions, environment descriptions were associated with each individual Object; now they may be described as Intellectual Entities and preserved as Representation, File or Bitstream Objects. Semantic units that are specific to Environment descriptions capture the function and designation of the Environment and may link to environment descriptions in external registries. Environments can be represented as aggregates or as individual components (e.g. an executable file, a stylesheet); therefore, relationships become crucial. A direct relationship between Agents and Objects will now be used to capture the Environment that acted as the Agent in an Event.
- Physical Objects can be described as Representations and related to digital Objects and are thus no longer out of scope for PREMIS descriptions.
- preservationLevelType is added as a new semantic unit to indicate the type of preservation functions expected to be applied to the object for the given preservation level. An example might be where the preservation level type is “bit preservation level” and the repository elaborates by assigning “low”, “medium” or “high”.
- agentVersion is added to the Agent entity to express the version of software Agents.
- compositionLevel is no longer restricted to an integer, so that “unknown” may be used if the information is not available. An unknown value may also apply to formatName, which is a mandatory semantic unit, for unidentified formats.
The PREMIS Data Dictionary for Preservation Metadata, Version 3.0 includes extensive discussion of the revised data model and the expanded description of environments in its Introduction and Special Topics sections.
To enable automated workflows, there are many PREMIS semantic units that recommend that the value be taken from a controlled vocabulary. In previous versions the Data Dictionary included suggested values; most of these were included in LC’s Linked Data Service for Authorities and Vocabularies. In this version, some examples rather than suggested values are given, and the semantic unit refers to the specific vocabulary in the id.loc.gov system. Additional terms will be added to accommodate the new or revised semantic units in version 3.0.
The PREMIS XML schema is undergoing revision and will be available in the near future. When a draft is available it will be announced, and PREMIS implementers are encouraged to experiment with it and provide feedback. In addition, the PREMIS OWL ontology will be revised to reflect these changes.
The PREMIS Data Dictionary for Preservation Metadata, Version 3.0 is available from: http://www.loc.gov/standards/premis/v3/.
PREMIS Editorial Committee, Library of Congress
June 10, 2015