It is the figure which is described by the notation or that notation in order draws the ER model and to display. In narrow sense the Peter chain of the advocate
) due to thing of the original notation is called, in a broad sense various notations which on the basis of that it expands & develop are.
The ? entity) the sign which shows something related to that (the relationship) as the figure which with the line which shows is connected. As for original notation, with the ER model in the seventies it is something which is proposed by the chain, but presently there are no times when it is used excessively, (there are times when it is made questions for information processing test).
, but the basis is expressed the substance which is the base element of the ER model (
Today, most the fact that it has spread IE (information engineering) is notation and IDEF1X. As for IE notation, data central approach ( ) the information engineering which is the development methodology which is based (IE) with the technique which is lectured as the notation in, also "the foot of the bird" is called commonly. As for the National form technical laboratory (NIST: National Institute of Standards and Technology) with being something which is standardized as FIPS 184, the relational database (RDB) to it is the technique which seriously considered mounting. These many ER modeling/are supported with the database design tool.
Example of IE notation
In addition, T shape of character ER
Watanabe system (the Watanabe happiness three person) and the like is known in US, ( ) that it is not the ER model.
As for the ER model originally, the concept which becomes independent from mounting (semantics) being something which aims toward the fact that the modeling is done at level, as for ERD it is the tool in order to draw the conceptual data model. But, when entity is fitted that way in the table of RDB, because it is convenient to, to survey the logical data model, the logical data model design, furthermore it came to the point of being diverted to also the physical data model design. You being done the reverse engineering using which deduces the logical model from the physical model with this it reaches the point of, but "it is original misuse", there is also the criticism that "original business analysis was done to become the ?".
As a ER modeling tool "AllFusion ERwin Data Modeler" is famous.