Over the past three decades of library automation, librarians have had the opportunity to become familiar with the basics of database management systems and their logic. Most database management systems in the bibliographic universe are conceptually based on the entity-relationship (E-R) model. The E-R model captures and preserves some of the important aspects of real-world semantics. Like most models of database management systems, this model is based on the concepts of “entity”, “relationships” and “attributes”.

Also applicable to bibliographic databases, the E-R approach is an attractive means for conceptual modelling within the bibliographic universe and has been applied by several librarians.

Some definitions

It is useful to briefly define some basic concepts that are important.

Bibliographic entity

General term to designate a work or any manifestation or part of a work that contains intellectual or artistic creation. It is an object of interest for users of the catalog and object of description in the bibliographic databases. The entity also encompasses individuals, corporate entities and subjects.

Bibliographic universe

The totality of the bibliographic entities and their relationships. In a sense, the bibliographic universe is made up of all types of intellectual or physical objects in any format that contain works of imagination as well as information.


A property or feature that is common to some or all instances of an entity. It is a piece of information associated with an entity or a relationship. For example, “title”, “language” and “reading level” are some of the attributes of the entity “work”. Entities are described and identified through their attributes.

Bibliographic list

Association between bibliographic entities that have common characteristics, such as the relationship between a person and a work or between a work and an article. The concept also applies to relationships between entities and their attributes and between attributes.

The Entity-Relationship Model

Over the past three decades of library automation, librarians have had the opportunity to become familiar with the basics of database management systems and their logic. Most database management systems are conceptually based on the entity-relationship model. The E-R model captures and preserves some of the important aspects of real-world semantics. Like most models of database management systems, this model is based on the concepts of “entity”, “relationships” and “attributes”.

Also applicable to bibliographic databases, the E-R approach is an attractive means for conceptual modelling within the bibliographic universe and has been applied by several librarians. No other conceptual models have been used to illustrate the bibliographic entities.

Problems and complexities of designing a common conceptual model

The question of whether or not to generalize a given model often arises for anyone trying to use E-R models as an analysis tool. This is partly due to the fact that the bibliographic universe itself is a complex environment that encompasses several entities at different aggregate levels. In addition, each category of library materials (i.e., bibliographic articles) is different in nature and attributes. For example, monographs differ from periodicals in that certain types of relationships (e.g., equivalence, derivation, and the whole part) are more common in them than in periodicals. Since the nature of each type of material is different from that of the others, the types of attributes and relationships of each category of library material are different and therefore require different treatments.

Bibliographic Entities

A clear identification of the entities is a first step in the conceptual analysis of the bibliographic universe. If we are going to identify various attributes of bibliographic entities and the relationships between them at different stages and create bibliographic records so that they can be functional in a multitude of environments, that is, from the creator to the publisher, through the printer, the distributor and the library, and in a local catalog, National or global, the first step is to define the different constituents of the bibliographic universe, such as “works”, “expressions”, “manifestations”, “articles”, “people”, “corporate entities”, etc. It will then be possible to design a conceptual framework for bibliographic entities to be described in any environment.

There is no defined terminology for the entities of the different bibliographic levels. In addition, the bibliographic vocabulary used by each community is somewhat different from that of other communities. In the library context the terms have been used, and are used, interchangeably.

There are at least four justifications for reaching a consensus on the definition of bibliographic entities:

1) Conceptual modeling of bibliographic entities would be easier and more understandable,

2) The growing possibility that the same work is produced in different manifestations and formats,

(3) The proliferation of shared cataloguing systems and joint databases that create and exchange bibliographic records, and

4) The trend towards the cooperative creation and use of bibliographic records by publishers, library providers and libraries, which requires simple and understandable definitions for all.


It is an abstract entity in text form consisting of a string of ordered symbols. The IFLA (International Federation of Library Associations and Libraries, IFLA)Study Group on Functional Requirements for Bibliographic Records defines the work as an abstract entity. In general, the abstract “work” is the basis of later expressions and manifestations.


Conceptually, “expression” indicates the next level in the bibliographic hierarchy and provides a link between a “work” and any “manifestation” based on that work. It is a specific presentation of the abstract work in the form of text (i.e. sequence of symbols, words, phrases) and/or illustrations, etc.

In the context of “expressions”, the term “edition” must be clearly defined because it is a term widely used in the treatment of the bibliographic universe. Defining what constitutes an “edition” is one of the most important requirements for any conceptual model of the bibliographic universe and also in the practice of cataloguing; there is no general consensus on such a definition.

Terms like “edit,” “reprint,” “reissue,” “number,” etc., have always been problematic for catalogers, especially in shared cataloging systems. In practice, the decision whether or not to create a new bibliographic record for the catalogued article depends on the definition of “edition”. A new edition can be defined as any significant change in the intellectual or artistic content or in the form and/or arrangement of a work that makes it different from another edition of that work. The modifications, revisions and translations are, therefore, new editions of the same work.


Conceptually, “manifestation” shows the transition from the abstract entity to the physical entity: any expression can potentially be embodied in different physical formats. Thus, manifestation is a general term that represents any kind of physical embodiment of an expression of a work.

It should be noted here that the term “version” has been used in literature interchangeably for the intellectual and physical forms in which an edition is produced and represented for use. For example, the same expression of a work can be represented in different physical formats, such as print and electronic, or the same work can be produced in various literary forms, for example, a version of “One Thousand and One Nights” for young readers. The problem of “multiple versions” refers to the description of different physical formats of (the same) work in a catalog.

Attributes of Bibliographic Entities

Entities and relationships are rated by attributes that represent their descriptive properties. Each entity has a set of attributes. Attributes can be considered as data elements associated with bibliographic entities to describe and clearly identify them during the processes of creation, publication, production and cataloguing. For example, the title of a work is an attribute that makes the work known to readers. To uniquely identify an entity, you can use a combination of attributes such as author name, title, edition, and publication date.

Even this combination may need further clarification, such as the format (for example, is it the paper or microfiche version?). One of the main concerns of cataloging codes has been, and continues to be, how to identify and register the least number of attributes necessary for proper identification and access to bibliographic entities in a catalog. “Proper identification” means sufficient information, such as content, reading level, document type, publication information and imprint, which helps users decide on one particular item over another and confirm that the item described is the one they are looking for in the catalogue.

Attributes of bibliographic entities in an online environment

It should be noted here that many of the following attributes have been used, at one time or another, as entry points into some manual catalogs. However, the concept of machine-readable registration has made it possible to include new attributes and/or new ways to make old attributes more easily recoverable. These attributes can be useful in an electronic environment and help identify, retrieve, organize, and display records based on users’ needs.

The language of the article, the reading level (i.e. the target audience), genre/form, document type or material category, physical format, geographic area code, standardized numbers, and registration number are attributes that, due to the limitations of the manual catalog, were not included in bibliographic records or were not usually search/retrieval items.

Bibliographic Relations

Entities do not usually exist in isolation, but are associated with each other through different types of relationships. In its simplest definition, bibliographic relationships are the associations between two or more entities in the hierarchy of the bibliographic universe. Any study of the bibliographic record must take into account the relationships that exist between the entities in the bibliographic universe and in the catalog that is a partial representative of that universe. The end result of these relationships and the purpose of bibliographic records is access to adequate and accurate information, to entities that meet information needs. The study of bibliographic relationships is fundamental to understanding the nature and structure of the bibliographic record, the catalogue and, ultimately, to the study of the principles of cataloguing.

Relationship types

In a broad sense, bibliographic relationships can be classified into two types: those between the entity and its attributes and between attributes (i.e. internal associations); and those between entities (i.e. external relationships). The principles and rules of cataloguing refer to both types of relationships.

Internal relations

In the first type of relationship, when a work is created by the creator (for example, the author), relationships are established between the creator and the work. Associations in data, such as “an author has written a book,” are called relationships. In this case, the relationship between the entity “author” and the entity “book” is “has written”. This type of bibliographic relationship forms the structure of the register and is an integral part of the bibliographic register. You cannot include any attributes in a record without it having associations with the entity itself. It is a simple but very important type of relationship in the bibliographic universe and to which cataloguing codes devote considerable attention.

Some types of internal connections are presented in turn in the log in the way that data elements are displayed relative to each other; for example, the relationship between the author and the title is maintained directly by displaying the author’s name near the title, either as the “main header of the entry” above the title or by repeating it with related words, such as “by”, “written by”, “editor:”, etc., such as the “statement of responsibility” following the title. Also, on the cover or in the main source of information, the author’s name usually appears near the title. Even if it doesn’t, the cataloger tries to establish this relationship in the record.

Adding more attributes

More attributes are added when the abstract “work” is embodied in an “article”. In this phase, attributes such as the place or places of publication, the name of the publisher or publishers, the date of publication, the length and size of the article and the international standard number of the book (ISBN) are introduced. The task of the cataloger is to identify various types of relationships and create bibliographic records based on a certain structure for the visualization of the relationships between the entity and its attributes and between the attributes, that is, the data elements.

External relations

Another important type of relationship, which is established in the initial phase but is often not clearly indicated by the creator, is the relationship between entities. It is the type of relationship that the cataloger tries to distinguish and describe according to the rules provided for in the cataloging codes. The relationship between a newly created work and the works of other authors that have been used as sources for the creation of the work is not usually defined, except by indicating a general note such as: “Includes bibliographic references”.

Bibliographic Relationships in an Online Environment

Bibliographic relationships are inherent in the bibliographic universe, and consequently in catalogues, and do not depend on the medium and environment in which records are created, manipulated and made accessible for search. New technology has made it possible for bibliographic relationships to be maintained and displayed more efficiently and flexibly in the online catalogue than was possible in the catalogue of files. In the last decade the interest in bibliographic relationships has been reborn and this may be the result of the impact of the online environment on the structure of library catalogs, bibliographic records and indexes within the catalog.

Moving to a shared online environment, such as shared cataloguing systems, collective catalogues and national or international networks, the need to express bibliographic relationships and types of partnerships has become more important, as it is likely that, with the increase in the number of participating libraries and library collections, increase the number of manifestations and editions of a work.

Relations between Entities

In this environment, it is important for the user to identify the relationship of the entities to each other and distinguish the place they occupy in the bibliographic hierarchy. For example, a problem for the user appears when the funds are related to works or articles that may be cataloged as collections or as separate parts (for example, an identical article cataloged as part of a series to which it belongs, or as a monograph in its own right).

However, with the advent of computerized catalogs, the concept of link devices has evolved little; many of the traditional devices have been reflected in online catalogs.

Changes from the traditional method

The traditional technique used to link records is to rely on data from records to establish relationships. On virtually all access points, the contents of the header field can be used to relate the record to other records with the same header. In today’s systems, data from binding fields is rarely used to establish a direct link between records. The search engine is expected to use information about related items as the basis for the subsequent search. However, the format supports more direct linking, and the possibilities deserve to be explored.

In an online environment, each type of relationship (i.e. bibliographic, name, subject and access point) can be established according to the structure, content and search retrieval capabilities of the computerized catalog. Online catalogs have the potential to provide visualizations of related bibliographic records, grouped according to the type of bibliographic relationships. What has been retrieved can guide the user in the subsequent search.

Some Outstanding Questions

With regard to the maintenance of bibliographic relationships, as well as the types and forms of linking devices, the question arises as to whether the rules of current cataloging codes are relevant to an online environment: do they give instructions on how to provide the most suitable devices for linking related records? Since catalog building technology determines the types of link devices (abandoning some, for example, hyphen entry, or introducing others, for example, standard numbers), should cataloging codes provide separate rules for bibliographic relationships and linking devices to take full advantage of the online environment?

Another question that seems relevant here is: what types of link devices to secure all types of bibliographic relationships are appropriate for an online environment? For example, the variety of linking devices for expressing part-everything relationships can be a critical issue for the online catalog. Is it possible and relevant to reduce this diversity in the treatment of relationships in an online environment? Is it possible to make a record for the whole and its parts, or to make multiple records? Can we then make each party have a separate record that cites the whole?

In this way, this is an important issue in a network environment. Library policies may differ from each other when describing the parts of a whole.

Problems with the MARC Format

The general approach to bibliographic records constructed with current cataloguing codes and MARC formats (Machine-Readable Catalographic Record, MARC) is not able to adequately maintain and display the different types of relationships. There is no clear and uniform approach to the treatment of different types of relationships. In many cases, as noted above, different devices are used to demonstrate the same type of relationship. For example, the equivalence relation can be displayed by different binding devices, such as dash entries; notes to recognize the equivalent copy; notes to recognize the original; shared uniform titles and stock declarations for copies.

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Anders ME, Evans DP: Comparison of PubMed and Google scholar literature searches. Respir care. 2010, 55: 578-583.

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You might also be interested in: Index of Bibliographic Citations or Citation Database

Bibliographic Universe and its management in the online world

Bibliographic Universe and its management in the online world. Source: Unsplash. Credits: Priscilla Du Preez @priscilladupreez

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