Eva Klein's picture

The ER diagram has been introduced by P. Chen in 1976 [Chen76] and has been widely used for conceptual data modeling ever since.Today, there are many variants of the ER diagram, four of them are available in ARIS (see Figure 1).

ER diagrams in ARIS

                                          Figure 1: ER diagrams in ARIS


The following table exposes which object types can be found in which ER diagram.

Object types in ER diagrams

When looking closely at this line-up, you can see the main differences between the ER model types in ARIS: the eERM uses the object type “relationship type” to model relationships between entity types. This object type is missing in IE data model, SAP SERM and SeDaM model, where relationships are represented by connection lines.

Another difference apparently refers to the modeling of attributes and their domains. This conclusion, however, is rather erroneous because all object types that may have attributes (entity type and relationship type) can be detailed by an eERM attribute allocation diagram.

The ER object types listed in the above table can be assigned to three layers representing different levels of detail (see Figure 2).

Hierarchy of ER object types
                                                Figure 2: Hierarchy of ER object types

In my future articles I will explain the following ER model types in more detail:

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