About the RDA Registry and vocabularies
Work on a draft version of the RDA element sets and value vocabularies began in 2008, following the Data model meeting at the British Library, London, England, between experts in RDA and related metadata communities. Since then a significant amount of discussion and learning has occurred. The current RDA vocabularies reflect that understanding.
The draft version of the elements available at http://rdvocab.info were never officially published, so those elements are deprecated and users and applications redirected to the published versions . A Map from deprecated to published RDA properties contains redirections for the most popular properties that have been deprecated; a Map from deprecated to published RDA classes contains redirections for all of the classes that have been deprecated.
In January 2014 the RDA vocabularies were made available in published form in the namespace http://rdaregistry.info/. This operational version of the elements has been extensively rearranged, and is updated as required to reflect decisions by the RDA Steering Committee (RSC).
The published vocabularies are currently available in several sets which reflect the underlying IFLA Library Reference Model. There is also a version for library and other users who prefer properties not locked-in to LRM. These "unconstrained" elements are in a separate set, but they have the same internal relationships as the elements in the "constrained" sets.
The RDA Development Team, with representation from RSC, TMQ, and American Library Association Digital Reference, works on extensions and refinements of the RDA element sets and value vocabularies. The RDA editor RIMMF (RDA in Many Metadata Formats) is developed by TMQ to use the vocabularies and other RDA Registry services. The Team is always happy to discuss current and future requirements of users or potential users of the vocabularies.
For further information about the development of the RDA vocabularies, see:
- Instructions, interfaces, and interoperable data: the RIMMF experience with RDA / Gordon Dunsire, Deborah Fritz, and Richard Fritz. Paper presented at IFLA WLIC 2016.
- Building a platform to manage RDA vocabularies and data for an international, linked data world / Jon Phipps, Gordon Dunsire, and Diane Hillmann. In: Journal of Library Metadata, v.15, issue 3-4 (2015), pp. 252-264. DOI: 10.1080/19386389.2015.1099990
- RDA and the semantic Web : lectio magistralis in library science : Florence, Italy, Florence University, 4th March, 2014 and the accompanying presentation by Gordon Dunsire.
- Seminar: Global Interoperability and Linked Data in Libraries, 18-19 June
2012, University of Florence. Italy.
- RDA and the Semantic Web, Linked Data Environment / Barbara Tillett
- Linked and open data: RDA and bibliographic control / Alan Danskin
- Five Years On - Background and Planning for the Future and the accompanying presentation. Presented by Dr. Barbara B. Tillett for the Seminar held at the British Library, London, April 27, 2012.
Please raise issues or make comments on the RDA Registry and vocabularies using the GitHub service at RDARegistry/RDA-Vocabularies Issues.
The development team monitors all issues and comments, and endeavours to respond as soon as it is able.
The RDA Registry data are updated at intervals, to reflect amendments to the content of RDA and its RDF representation for linked data applications.
Good practice policies are applied to the management of versions and releases, and the deprecation of elements and concepts.
Versions and Releases
Any change to the vocabularies that is published to GitHub will result in a new version being assigned. The version designations follow the general principals of Semantic Versioning, resulting in a 3-tier numbering system:
- A change that has no effect on the semantics of any Element will result in a 'patch' version that will increment the third segment of the number: "1.1.X"
- A change that affects the semantics of any property of any Element will result in a 'minor' version that will increment the second segment "1.X.0", and reset the third segment to 0
- A change that breaks backwards semantic compatibility will result in a 'major' version change that increments the first segment "X.0.0", and resets the other segments to 0. We expect major versions to be extremely rare.
Every time a release is pushed to GitHub, it is tagged with the version number of the release. GitHub recognizes any tag as a release and takes a snapshot of the state of the entire repository at the point in time that the tag was applied. GitHub then creates downloadable zip and tar files for that snapshot. It also makes it possible to reference the snapshot with a specific IRI.
The master branch of the repository will always have the latest version, which
will always have a version tag. The current version can also be referenced by
checking the contents of the
version file in the root directory of
the repository. When appropriate, a list of the changes will be added to the
The list of releases, along with the downloadable files and reference URLs are available here: https://github.com/RDARegistry/RDA-Vocabularies/releases.
Classes, properties, concepts
The removal of an entry from the RDA elements will be treated as a deprecation of the relevant class, property, or concept from RDA Reference. A Registry status of "Deprecated" will be assigned.
The text "(Deprecated)" is added to the labels and definitions of a deprecated class, property, or concept.
Ontological statements about RDA classes, properties, or concepts (sub-properties, domains, etc.) will be assigned a Registry status of "Deprecated" when necessary, or as a result of changes to the RDA elements, or to rectify errors.
Registry statements with status "Deprecated" are included in the direct RDF/XML output of the ALA Staff Registry and subsequent versions of the RDA vocabularies.
Applications may filter deprecated data using the Registry status or the presence of the fixed text in labels and definitions.
RDA Reference includes all RDA Elements, their definitions and any related scope notes, and all value vocabulary terms and definitions.
RDA Elements include entities, attributes, and relationships described in RDF. The value vocabularies include the controlled terminologies for RDA data given in the Toolkit instructions, and a controlled terminology used with the instructions in general. These are described as Simple Knowledge Organization System (SKOS) Concepts in RDF.
Data flow and maintenance
ALA Staff Registry
RDA Reference data are stored in the ALA Staff Registry in Resource Description Framework (RDF).
The data are exported in multiple RDF formats, or serializations, to a GitHub open file repository with version control named RDA Vocabularies. Each export is a cumulative snapshot of the ALA Staff Registry data. Specific snapshots are designated as releases and given a semantic version number.
RDA Vocabularies (GitHub)
GitHub makes all releases and snapshots available for download, so applications can freeze or roll-back the data.
GitHub also makes all release and change notes available, along with automatic change comparison documentation.
GitHub offers an open active issue management system, used by RDA developers to raise queries, notify errors, and make suggestions for improvement.
The RDA Registry provides links to download the individual element sets and value vocabularies in the current release of RDA Vocabularies.
The Registry offers additional documentation and tools to RDA developers. These include examples of RDA linked data and machine-actionable maps for transforming RDA data for use by non-RDA applications.
The RDA Registry also provides updated data to the RDA Vocabulary Server whenever a new release is published.
RDA Vocabulary Server
The Vocabulary Server provides a de-referencing service for RDA IRIs used in linked data, serving RDF serializations of the vocabularies in response to requests from applications.
The Server runs several services that provide language-specific extractions from the 'all-languages' vocabulary serializations available from the RDA Registry, based on specific requests for one or more languages.
Services also extract individual Elements and Concepts/Values from the broader element sets and value vocabularies in order to provide RDF representations of specific IRIs.
Element references, broader and narrower element navigation, element browse, vocabulary encoding schemes, and the glossary in RDA Toolkit is based entirely on RDA Reference data.
The RDF/XML serialization available in the current release of RDA Vocabularies is processed with a transform script to extract the relevant data and format it in DITA XML for the Toolkit Content Management System.
RIMMF3 provides active links from its RDA data input forms to the instructions in RDA Toolkit.
The ALA Staff Registry allows data to be updated under password control through a batch file import facility within an administrator interface.
Single Element and Concept updates
Updates to single elements and concepts are made through a private content management system which allows the RSC Technical Team Liaison and the RSC Secretary to update individual Elements and Concepts/Values, including additions, amendments, and deletions.
The ALA Staff Registry has a data import facility that allows for the updating of one or more element sets or value vocabularies. The facility requires both a password and authorization. The data are imported as csv files.
The ALA Staff Registry rejects malformed data.
The batch update procedure is also used for translations of RDA Reference.
Data flows from the ALA Staff Registry to the RDA Vocabularies GitHub repository as snapshots. The RDA Vocabularies files are openly available.
The primary users of the RDA Vocabularies files are:
- Element reference for RDA elements in RDA Toolkit
- Broader and narrower elements navigation in RDA Toolkit
- Element browse in RDA Toolkit
- Vocabulary encoding schemes in RDA Toolkit
- Glossary in RDA Toolkit
- RDA Registry
- RDA Vocabulary Server
RDA data flow diagram.
RDA Reference includes the RDA element sets and value vocabularies.
Official, full translations of RDA Toolkit must allow the RDA Reference translations to be published in the RDA Registry, under an open license (CC BY 4.0). Note that this license allows commercial re-use, to encourage development of applications using RDA linked data.
The addition of less-than-full translations of RDA that cover all or part of RDA Reference is welcome, if the translation is maintained by an RDA user community or individual authorized by ALA Digital Reference.
Contact ALA Digital Reference for further information about full translations of RDA Toolkit that include the RDA guidance and instructions.
The RDA Registry uses linked data representations of RDA Reference in Resource Description Framework (RDF) managed in the ALA Staff Registry, and provides maps from RDA data to other schema.
Adding and updating translations in the ALA Staff Registry are done by the RSC Translations Working Group.
Applications of RDA Reference data
The RDA vocabulary management infrastructure was developed so that RDA Reference data are maintained in one place and distributed for use in RDA Toolkit, RDA Vocabularies (GitHub), RDA Registry, and external applications such as RIMMF (RDA in Many Metadata Formats).
Much of the content of the Toolkit is based exclusively on the RDA Reference data published in RDA Vocabularies, including element references, broader and narrower element navigation, element browse, vocabulary encoding schemes, and the glossary.
RDA Toolkit uses the RDA Reference data workflow for all language versions of RDA Toolkit.
RDA Vocabularies, the RDA Registry, and RIMMF use all of the translation data.
The RDA Registry offers interactive user control of data display of individual element sets and value vocabularies in every language available in the current version of RDA Vocabularies. For an example with many translations, see RDA Content Type.
RIMMF offers static user control of data display of the elements and values as a whole in every available language. The facility is available via the RIMMF menu: Options > Setup > Set language and labels. The Update language data button ensures that translations from the current version of RDA Vocabularies are used.
The RDA Registry and RIMMF both default to English if a translation in the selected language is not available.