IFLA Library Reference Model

“The IFLA Library Reference Model aims to be a high-level conceptual reference model developed within an enhanced entity-relationship modelling framework. The model covers bibliographic data as understood in a broad, general sense. In terms of general approach and methodology, the modelling process that resulted in the IFLA LRM model adopted the approach taken in the original FRBR study, where it was described as follows: "‘The study uses an entity analysis technique that begins by isolating the entities that are the key objects of interest to users of bibliographic records. The study then identifies the characteristics or attributes associated with each entity and the relationships between entities that are most important to users in formulating bibliographic searches, interpreting responses to those searches, and ‘navigating’ the universe of entities described in bibliographic records. The model developed in the study is comprehensive in scope but not exhaustive in terms of the entities, attributes, and relationships that it defines. The model operates at the conceptual level; it does not carry the analysis to the level that would be required for a fully developed data model.’” (FRBR, p. 4)"

Class or “isA” Hierarchy for Entities
The model includes a single top-level entity (res), shown in the first column of the table; all other entities are direct or indirect subclasses of res. The eight entities that are direct subclasses of res are shown in the second column: work, expression, manifestation, item, agent, nomen, place, time-span. The third column shows the two entities that are subclasses of the entity agent: person and collective agent.

Entities Detailed Definition
Each entity declared in the model is described in the table below. Entities are numbered sequentially from LRM-E1 to LRM-E11. Following the number, first the name of each entity is given, then a brief definition, and a statement of relevant constraints, all in the same row. A longer scope note and a selection of examples of instances of that entity are in subsequent table rows. To fully understand the intent of each entity, and the kinds of instances that belong to it, it is important to consult the definition and the full scope note. The names of the entities are to some extent arbitrary, they are intended to serve as shorthand to refer to the entities in the sections on attributes and relationships that follow. The name of an entity viewed alone is not intended to convey the full meaning behind the entity.

In considering the examples of all the entities other than the entity nomen, it is important to bear in mind that instances of entities need to be referred to by a nomen associated with that instance, but it is the instance itself which is the example, not the nomen. When necessary to highlight the distinction between a res and a nomen representing the res, a description of the instance of the res entity is given in curly braces ({ }), while a term representing an instance of the nomen entity is given in single quotes (' '). Additionally, where the distinction is necessary, straight double quotes (" ") indicate a value of the nomen string attribute of an instance of the nomen entity.