1. Extending RDA (briefly)
Gordon Dunsire
Presented to the RDA "pop-up" meeting, ALA Annual, Chicago, USA, 26 June 2017
This is a brief presentation on basic ways of extending RDA to accommodate the needs of local and specialized communities.

2. RDA entities RDA Entity Nomen W Place E Agent Time-span M Collective
Any RDA Thing:
Covers all other types of entity
RDA entities
RDA
Entity
has appellation
Nomen W
is created by
Place E
Agent
is associated with
is sub-class of
Time-span M
Collective
Agent
This diagram shows how RDA is a refinement of th new IFLA Library Reference Model (LRM).
RDA Entity is a super-entity of all other RDA entities. RDA Entity is a sub-type (sub-class in RDF) of the LRM super-entity Res.
This RDF graph shows new RDA entities taken from the LRM: Nomen, Place, Time-span, Collective Agent, and Agent. Current RDA entities are labelled only with their initials. The graph also shows the high-level relationships between the new and current entities.
The only RDA entity which does not fit without significant modification is Person. In the LRM, the definition of this entity restricts it to a human being, and non-humans including animals, fictitious and legendary beings, and natural phenomena, are excluded.
The integrated semantic structure of the LRM and RDA entities allows the RDA relationships to be refinements of the high-level LRM relationships, as element sub-types (sub-properties in RDF). I
RDA refines LRM relationships as element sub-types (RDF sub-properties)
is modified by P* F C

3. Adding entities RDA entity RDA Toolkit chapter Standard elements:
Identifier of …
Name or title of …
Association relationships
with other entities …
RDA Toolkit files
(+ Registry stuff)
Refining or extending RDA by adding a new entity requires justification and careful consideration.
Each entity will have a chapter of its own in the restructured RDA Toolkit.
Most RDA entities have a standard set of elements, such as "Identifier of entity" and "Name or title of entity). All RDA entities have a set of high-level relationships with each other. These elements are added for each new entity, requiring updates to RDA Reference, the RDA Registry, and the RDA Toolkit.
These are significant costs, and the benefits to RDA users as a whole must be demonstrated with use cases and other evidence.
Requires justification,
use cases, etc.
Expensive!

4. Extending element sets
Element = attribute/relationship (designator)
RDA Element Set
RDA Element
Alternative label
The element set for an entity can be extended by:
Adding a local label to an element as an alternative label
Refining an element by creating an element sub-type (sub-property in RDF linked data)
It is also possible to add a new element to an element set.
Narrower element

5. Extending value vocabularies
RDA Vocabulary
Alternative vocabulary
RDA Term/Concept
Alternate label
Extending an RDA value vocabulary can use similar methods.
A local label can be used as an alternate label for a vocabulary term or concept, or a narrower term or concept can be added to the vocabulary.
RDA also allows a complete alternative vocabulary encoding scheme or value vocabulary to be used if it is named or otherwise identifiable.
The RDA Development Team is looking into support for the management of local alternative vocabularies.
Narrower term