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Chapter 8. Resource Description and Access - Official: Basics, Describing RDA Entities: Work, Expression, Manifestation, and Item

Chapter Outline

  • R3 Project


  • Official RDA Basics

  • Describing Entities

  • RDA Entity

  • Works

  • Expressions

  • Manifestations

  • Items

Key Takeaways

Chapter 8 starts with a discussion of basic concepts from the IFLA LRM conceptual model and the new version of RDA, the official RDA.  It also includes an overview of entity description, types of elements, and in particular the description (only select elements) of the entities RDA entity, work, expression, manifestation, and item.


The IFLA Library Reference Model, the new conceptual model, is a harmonization and replacement of the three FR models (FRBR, FRAD, FRSAD). LRM serves as the theoretical foundation for the official RDA.

LRM entities

LRM introduces the top-level entity Res, under which all other LRM entities are defined. Three levels of entities are defined: at the top level is Res; at the second level eleven entities are defined as subclasses of Res and include work, expression, manifestation, item, agent, nomen, place, and time-span; and at the third level two subclasses of the agent entity are defined to include person and collective agent. In addition, the most essential attributes and relationships are defined in IFLA LRM. Any particular implementation of LRM can define additional subclasses, attributes, and relationships to meet the needs of their information community. 

Official RDA

The official RDA was released in December of 2022 to align with the IFLA LRM. This is the RDA version that continues to be developed. The original RDA has not been maintained since its last revision in April 2017, and plans are in place to remove it from the RDA Toolkit in the near future.

Some new official RDA terms

element: a specific aspect, characteristic, attribute, or relationship used to describe an RDA entity; there are two kinds of elements - attribute element and relationship element.

metadata statement: the value for an element describing an instance of an RDA entity. A metadata description set is one or more metadata statements used to describe and relate an RDA entity instance.

vocabulary encoding scheme:  lists of controlled values (terms, codes, etc.) for elements. For example, the list of RDA content type terms. 

range and domain: Domain indicates the RDA entity an element is describing; range indicates the RDA entity that is the value of a relationship element. All elements have a domain but only relationship elements have a range. For example, in the statement "London is the related place of person Adam Smith," the relationship element "related place of person" describes an instance of the entity person (domain) and the value of this relationship element is a particular instance of the entity place (range).

Official RDA changes

Official RDA changes (compared to the original RDA) include a new content structure organized by entities; the definition of RDA entity (in place of LRM Res with some modifications); and a total of thirteen entities defined, which include RDA entity, work, expression, manifestation, item, agent, collective agent, person, corporate body, family, nomen, place, and timespan. Note that as per LRM, nomen is an entity in the official RDA. An appellation relationship exists between an RDA entity and a nomen, for example, person "has appellation" nomen.

The official RDA includes fewer instructions on how to describe resources and therefore it is necessary for communities to develop application profiles when using the official RDA.

Unlike the original RDA, in the official RDA elements are defined for both attributes and relationships - therefore elements can be attribute elements and relationship elements. The result is a very large number of RDA elements.

Four methods for recording element data are defined: structured description, unstructured description, use of identifiers, and using IRIs (Internationalized Resource Identifiers). 

Official RDA entity description

A minimum description of an RDA entity should include at least one "appellation of RDA entity" element, whether a name (e.g., preferred name of RDA entity), access point (e.g., authorized access point for RDA entity), or identifier. An effective description of an RDA entity should include all the elements necessary for the identification and access of this entity. 


For each entity, RDA includes an “entity boundary” which guides how to describe entities. An RDA entity boundary is a set of criteria specific to each entity that helps the metadata creator decide if a description of a new entity is required or if different entities need to be included in an application profile. 

Chapter References/Notes

  1. RDA: Resource description and access. (2019). Developed in a collaborative process led by the Joint Steering Committee for Development of RDA (JSC). Chicago: American Library Association

  2. IFLA Functional Requirements for Bibliographic Records (FRBR) Review Group. (2018). IFLA library reference model: A conceptual model for bibliographic information. Retrieved from

  3. RDA Toolkit 3R Project. (2020). Retrieved from

  4. RDA Steering Committee. (2022). RDA FAQ. Retrieved from

  5. RDA Steering Committee. (2022). RDA FAQ: What is different between the two versions? Retrieved from

  6. RSC. RDA Steering Committee. (2021). 3R project final report.

  7. RDA Toolkit Instruction Identification. (2018, July 30). Retrieved from 30 July 2018, on RSC website:

  8. RDA Board. (n.d.). Strategic plan for RDA 2020-2022. Retrieved from

  9. RDA Toolkit. (n.d.) Glossary. Retrieved from

  10. Parent, Melissa. (2021, December 2). A primer on RDA application profiles. Retrieved from specifies,terms%2C%20an%20AP%20specifies%20obligation.

  11. International Committee for Documentation (CIDOC). (n.d.). Conceptual reference model (CRM). Retrieved from

  12. World Wide Web Consortium (W3C). (2021, December 13). Simple knowledge organization system (SKOS). Retrieved from


Additional Readings

Here, you will find readings specific to the contents of this chapter.

You may find more readings about similar topics on the Cataloging and Classification Web Resources and External Training Resources pages

Bibliographic Relationships
  • Holden, C. (2021). "The bibliographic work: History, theory, and practice." Cataloging & Classification Quarterly, 59(2-3), 77-96, DOI: 10.1080/01639374.2020.1850589

  • Tillett. B. B. (2001). “Bibliographic relationships.” In Relationships in the Organization of Knowledge, Kluwer Academic Publishers, 19-35. 

RDA and the RDA Toolkit
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