entity-relationship model

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entity-relationship model

(database, specification)
An approach to data modelling proposed by P. Chen in 1976. The model says that you divide your database in two logical parts, entities (e.g. "customer", "product") and relations ("buys", "pays for").

Entity-relationship diagrams can be used to represent a model.

["The entity-relationship model: toward a unified view of data", P.P. Chen, ACM Transactions on Database Systems 1:1 pp 9-36, 1976].
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)
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Using a simple example (see Figure 1), the teaching module introduces ER (entity-relationship) diagrams and emphasizes that MBA BA students should be able to read ER diagrams because an ER diagram is the blueprint of a database and can help users navigate the entire database when extracting needed data sets for BA.
The teaching module then presents the database implemented in Microsoft Access in accordance with the ER diagram of the example and demonstrates how one can navigate the database through visualizing the implemented entity relationships inside the database (see Figure 2) to extract needed data sets from the database for BA.
According to this ER diagram, tables are created for the following entities (Longley et al.
According to this ER diagram, tables are created for the following entities: service laterals, clean outs, gravity mains, lift stations, manholes, abandoned lines, wet wells, abandoned points, monitor locations, and service mains.
To its credit, this ER diagram portrays the domain in a way that is independent of the target software platform.
Conversion of the ER diagram to a star schema is a step-by-step process and usually begins with a conversation between end users and IT professionals to discover a list of burning questions.
Build data tables (relations) from the ER diagram constructed in steps 1 to 5.
The function tree and ER diagram are then correlated by means of an entity-function table that shows the use that each business process makes of business data.
For example, the schema of the personnel database may be initially described using the entity-relationship data model in the form of an ER diagram. It may then be mapped into the relational data model which uses structured query language (SQL)--an emerging standard, to define the schema.
For example, as soon as the database requirement specification is available, an ER diagram for the target database could be easily developed.
It also provides an ER modeling workspace where students create ER diagrams. The lower window displays feedback from the system in textual form.
The practice of systems analysis was characterized 10 years ago by a mixed bag of isolated modeling techniques (data flow diagrams, ER diagrams, state transition diagrams) that were used to capture the rich information that needs to be modeled, analyzed and understood before a software system is actually built.