The ERD (Entity Relationship Diagram) is a logical (schematic) data model construction technique used with a specific IS (or by the entire organization). An ERD places particular emphasis on identifying primary data entities and the type of relationship between them. The ERD not only specifies the quantitative relationship between entities (one to one, one to many etc.) but also the significance of this relationship ("belongs to", "reports to" etc.). The ERD allows clear identification of key fields (link fields) and also supports the accessing of normalized files. The Data Entity is the "atom" of the model: a data object identified by key field/s and described by additional field attributes (solely) dependent on that object. The complete set of data for the Data Entity (a collection of all the fields) is a record in a normalized file.

• See also Component 2.11 (Data Modeling) in the SCT