07-30-2010, 05:54 PM
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"We use ER Data Model in conceptual database design instead of using other models but we never use ER data model in our logical database design"
In software engineering, an entity-relationship model (ERM) is an
abstract and conceptual representation of data. Entity-relationship
modeling is a database modeling method, used to produce a type of
conceptual schema or semantic data model of a system, often a relational
database, and its requirements in a top-down fashion. Diagrams created
by this process are called entity-relationship diagrams, ER diagrams, or
Entity-Relationship Modeling
The Entity-Relationship Model model serves as the foundation of many
systems analysis and design methodologies, computer-aided software
engineering (CASE) tools, and repository systems. The ER Model is the
basis for IBM's Repository Manager/MVS and DEC's CDD/Plus.
Dr. Peter Chen's original paper is commonly cited as the definitive
reference for Entity Relationship Modeling. Chen did not in fact invent
the concept; the basic ideas appear in earlier papers especially by
practitioners, such as that by A. P. G. Brown.[ However, Chen did more
than anyone to formalize and popularize the model, and to introduce it
to the academic literature.
The ER Model was adopted as the meta model ANSI Standard in
Information Resource Directory System (IRDS), and the ER approach
has been ranked at the top methodology for database design and one of
the top methodologies in systems development by several surveys of
Fortune 500 companies.[