Entity Relationship Modeling is the most common way to express the analytical result of an early stage in the construction of a new database (Pedersen 2010).
Entity-Relationship (ER-model) is a data model that is used to describe the conceptual schema. It is a graphical notation based on the blocks and connecting lines that can be used to describe objects and relations among them to any other data model. In this sense, the ER-model is a meta-data model, the mean for describing data models.
ER-model was proposed in 1976 by Peter Pin-Shen Chen - an American professor of computer science at Louisiana State University.
ER-model is widely used in Database system. It is convenient for prototyping (design) information systems, databases, architectures, computer applications and other systems (models). With the help of it, it is possible to identify key entities that are present in the model, and identify relationships that may be established between these entities.
ER-model is one of the simplest visual models of data (graphical notation). It allows defining the structure with "large strokes”, in general terms.
In the conceptual database schema, ER-models are widely used in CASE systems, supporting automated design of relational databases. Among the great quantity of ER-models notations, one of the most developed is Unified Modeling Language (UML). It is used in the CASE system of ORACLE. UML notation is also used by: Borland Software Corporation, University of Bremen, the University of Kent, University of York and Dresden University of Technology.
In 2005, the project "Design-Level LINUX Documentation" presented the most comprehensive analysis of the structure of the Linux kernel version 2.6 in the representation of UML 2.0. In this document, for each of the basic subsystems of the kernel (memory management, filesystems, security, cryptography, initialization, drivers, architecture and interprocess communication), the detailed description of the structure and relationships of components is presented.
So, the entity-relationship modeling is the way of graphically representing the logical relationships of entities (or objects) in order to create a database (Ramakrishnan 2008).
Pedersen, Alf A. "Entity Relationship Modeling." Programming Help, Web Design Help, CSS Help - Dev Articles. Web. 26 Oct. 2010. <http://www.devarticles.com/c/a/Development-Cycles/Entity-Relationship-Modeling/>.
Ramakrishnan, Jay. "The Entity-Relationship Model." Database Management Systems. Web. 25 Oct. 2010. <http://www.itu.dk/~pagh/DBSE06/ER-RG.pdf>.