The enhanced entity–relationship (EER) model (or extended entity–relationship model) in computer science is a high-level or
conceptual
Conceptual may refer to:
Philosophy and Humanities
*Concept
*Conceptualism
*Philosophical analysis (Conceptual analysis)
*Theoretical definition (Conceptual definition)
* Thinking about Consciousness (Conceptual dualism)
*Pragmatism (Conceptual p ...
data model incorporating extensions to the original
entity–relationship (ER) model, used in the design of
databases.
It was developed to reflect more precisely the properties and constraints that are found in more complex databases, such as in engineering design and manufacturing (
CAD
Computer-aided design (CAD) is the use of computers (or ) to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve c ...
/
CAM
Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the bin ...
),
telecommunications, complex
software systems
A software system is a system of intercommunicating components based on software forming part of a computer system (a combination of hardware and software). It "consists of a number of separate programs, configuration files, which are used to ...
and
geographic information systems (GIS).
Mechanics
The EER model includes all of the concepts introduced by the ER model. Additionally it includes the concepts of a
subclass and
superclass (
Is-a), along with the concepts of
specialization
Specialization or Specialized may refer to:
Academia
* Academic specialization, may be a course of study or major at an academic institution or may refer to the field in which a specialist practices
* Specialty (medicine), a branch of medical ...
and
generalization. Furthermore, it introduces the concept of a
union
Union commonly refers to:
* Trade union, an organization of workers
* Union (set theory), in mathematics, a fundamental operation on sets
Union may also refer to:
Arts and entertainment
Music
* Union (band), an American rock group
** ''U ...
type or category, which is used to represent a collection of objects that is the union of objects of different
entity types. EER model also includes EER diagrams that are conceptual models that accurately represent the requirements of complex databases.
Subclass and superclass
Entity type Y is a subtype (subclass) of an entity type X if and only if every Y is necessarily an X. A subclass entity inherits all
attributes and
relationships of its superclass entity. This property is called the attribute and relationship inheritance. A subclass entity may have its own specific attributes and relationships (together with all the attributes and relationships it inherits from the superclass). A common superclass example is a Vehicle superclass along with the subclasses of Car and Truck. There are a number of common attributes between a car and a truck, which would be part of the superclass, while the attributes specific to a car or a truck (such as max payload, truck type...) would make up two subclasses.
Tools
*The
MySQL Workbench offers creating, editing and exporting EER Models. Exporting to PNG and PDF allows easy sharing for presentations.
*
Skipper allows users to create, import and export from ORM schema definitions to editable EER models.
*SAP
PowerDesignerSAP PowerDesigner
/ref> is a complex tool for modelling and transforming different models.
See also
* Object–relational database
* Slowly changing dimension
* Structured type
References
Further reading
Textbooks discussing EER and implementation using purely relational databases:
*
*
*
Booklet discussing EER and implementation using object-oriented and object–relational databases:
*
Textbook discussing implementation in relational and object–relational databases:
*
Shorter survey articles:
*
*
External links
- Slides for chapter 8 from Fundamentals of Database Systems by Elmasri and Navathe (Pearson, 2011)
- Lecture notes from the University of Toronto
- The ER Conference
Data modeling diagrams
Data modeling languages
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